Reflective mask blank, reflective mask, and methods for producing reflective mask and semiconductor device

ABSTRACT

Provided is a reflective mask blank with which it is possible to further reduce the shadowing effect of a reflective mask, and also possible to form a fine and highly accurate phase-shift pattern. A reflective mask blank having, in the following order on a substrate, a multilayer reflective film and a phase-shift film that shifts the phase of EUV light, said reflective mask blank characterized in that: the phase-shift film has a first layer and a second layer; the first layer comprises a material that contains at least one element from among tantalum (Ta) and chromium (Cr); and the second layer comprises a metal-containing material that contains ruthenium (Ru) and at least one element from among chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2019/020635, filed May 24, 2019, which claims priority to JapanesePatent Application No. 2018-100363, filed May 25, 2018, and claimspriority to Japanese Patent Application No. 2018-165248, filed Sep. 4,2018, and the contents of which are incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a reflective mask blank that is anoriginal plate for manufacturing an exposure mask used for manufacturinga semiconductor device, a reflective mask, a method of manufacturing thereflective mask, and a method of manufacturing a semiconductor device.

BACKGROUND ART

Types of light sources of exposure apparatuses in manufacturingsemiconductor devices have been evolving while wavelengths thereof havebeen shortened gradually like a g-line having a wavelength of 436 nm, ani-line having a wavelength of 365 nm, a KrF laser having a wavelength of248 nm, and an ArF laser having a wavelength of 193 nm. In order toachieve further finer pattern transfer, extreme ultra violet (EUV)lithography using EUV having a wavelength in the neighborhood of 13.5 nmhas been developed. In the EUV lithography, a reflective mask is usedbecause there are few materials transparent to EUV light. Thisreflective mask has a basic structure in which a multilayer reflectivefilm that reflects exposure light is formed on a low thermal expansionsubstrate and a desired pattern for transfer is formed on a protectivefilm for protecting the multilayer reflective film. In addition, typicalexamples of the structure of the pattern for transfer include a binarytype reflection mask and a phase shift type reflection mask (a half-tonephase shift type reflection mask). The binary type reflection mask has arelatively thick absorber pattern that sufficiently absorbs EUV light.The phase shift type reflection mask has a relatively thin absorptionpattern (a phase shift pattern) that reduces EUV light by lightabsorption and generates reflected light having a phase substantiallyinverted (a phase inverted by approximately 180 degrees) with respect toreflected light from the multilayer reflective film. This phase shifttype reflection mask has a resolution improving effect because hightransfer optical image contrast can be obtained by a phase shift effect,as with a transmission type optical phase shift mask. In addition, sincethe film thickness of the absorber pattern (the phase shift pattern) ofthe phase shift type reflection mask is thin, a fine and highly accuratephase shift pattern can be formed.

In the EUV lithography, projection optical systems including a largenumber of reflecting mirrors are used due to light transmittance. Then,EUV light is made obliquely incident on the reflective mask to causethese reflecting mirrors not to block projection light (exposure light).At present, an incident angle is typically 6 degrees with respect to avertical plane of a reflection mask substrate. Along with theimprovement of a numerical aperture (NA) of the projection opticalsystem, studies are being conducted toward making the incident angleabout 8 degrees that is a more oblique incident angle.

In the EUV lithography, since the exposure light is obliquely incident,there is a specific problem called a shadowing effect. The shadowingeffect is a phenomenon in which exposure light is obliquely incident onan absorber pattern having a three-dimensional structure, whereby ashadow is formed and a dimension and position of a transferred andformed pattern change. The three-dimensional structure of the absorberpattern serves as a wall to form a shadow on a shade side, and thedimension and position of the transferred and formed pattern change. Forexample, a difference occurs in a dimension and position of a transferpattern between both cases, a case where the orientation of the absorberpattern to be arranged is parallel to a direction of obliquely incidentlight and a case where the orientation of the absorber pattern to bearranged is perpendicular to the direction of the obliquely incidentlight, thereby decreasing transfer accuracy.

Patent Literatures 1 to 3 disclose techniques related to such areflective mask for EUV lithography and a mask blank for manufacturingthe same. In addition, Patent Literature 1 also discloses a shadowingeffect. By using a phase shift type reflection mask as a reflective maskfor EUV lithography, the film thickness of a phase shift pattern is maderelatively thinner than the film thickness of the absorber pattern ofthe binary type reflection mask, whereby a decrease in the transferaccuracy due to the shadowing effect is reduced.

CITATION LIST Patent Literature

Patent Literature 1: JP 2010-080659 A

Patent Literature 2: JP 2004-207593 A

Patent Literature 3: JP 2009-206287 A

DISCLOSURE OF THE INVENTION

The finer the pattern is and the more the accuracy of the patterndimension and pattern position is improved, the more the electricalcharacteristics and performance of the semiconductor device increase,and the degree of integration can be improved and a chip size can bereduced. Thus, the EUV lithography is required to have performance oftransferring dimension patterns that are more accurate and finer thanconventional ones. Formation of an ultra-fine and highly accuratepattern for half pitch 16 nm (hp 16 nm) generation is presentlyrequired. A further reduction in the film thickness of an absorber film(a phase shift film) is required in order to reduce the shadowing effectin response to such a requirement. In particular, in the case of EUVexposure, the film thickness of the absorber film (the phase shift film)is required to be less than 60 nm and preferably 50 nm or less.

As disclosed in Patent Literatures 1 to 3, Ta has been conventionallyused as a material for forming the absorber film (the phase shift film)of a reflective mask blank. However, a refractive index n of Ta in EUVlight (for example, with a wavelength of 13.5 nm) is approximately0.943. Thus, even if the phase shift effect of Ta is used, the lowerlimit of the film thickness of the absorber film (the phase shift film)formed of Ta alone is 60 nm that is the lowest. For example, a metalmaterial having a small refractive index n (having a large phase shifteffect) can be used in order to further reduce the film thickness. As ametal material having a small refractive index n at a wavelength of 13.5nm, there are Mo (n=0.921) and Ru (n=0.887) as described, for example,in FIG. 7 of Patent Literature 1. However, Mo is easy to oxidize andthere is a concern about cleaning resistance, and Ru has a low etchingrate and is difficult to process and repair.

In view of the points described above, it is an aspect of the presentdisclosure to provide a reflective mask blank capable of reducingfurther a shadowing effect of a reflective mask and forming a fine andhighly accurate phase shift pattern and a reflective mask manufacturedusing the reflective mask blank and to provide a method of manufacturinga semiconductor device.

In order to solve the above problems, the present disclosure has thefollowing configurations.

(Configuration 1)

A configuration 1 of the present disclosure is a reflective mask blankcomprising a multilayer reflective film and a phase shift film forshifting a phase of EUV light on a substrate in this order, the phaseshift film comprises a first layer and a second layer, the first layercomprises a material containing at least one or more elements oftantalum (Ta) and chromium (Cr), and the second layer comprises amaterial comprising a metal containing ruthenium (Ru) and at least oneor more elements of chromium (Cr), nickel (Ni), cobalt (Co), vanadium(V), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re).

According to the configuration 1 of the present disclosure, it ispossible to obtain a phase shift film having thin film thicknessnecessary for reflected light from a phase shift pattern to have apredetermined phase difference as compared with reflected light from anopening of a reflective mask pattern. Thus, a shadowing effect caused bythe phase shift pattern can be further reduced in a reflective mask. Inaddition, according to the configuration 1 of the present disclosure, itis possible to obtain a phase shift film having high relativereflectance (relative reflectance when EUV light reflected at a partwhere the phase shift pattern is not present is assumed to be 100%reflectance). In addition, a reflective mask manufactured from areflective mask blank having the configuration 1 of the presentdisclosure is used, whereby it is possible to improve throughput when asemiconductor device is manufactured.

(Configuration 2)

A configuration 2 of the present disclosure is the reflective mask blankaccording to the configuration 1, in which the second layer comprises amaterial comprising a metal containing ruthenium (Ru) and at least oneor more elements of chromium (Cr), nickel (Ni), and cobalt (Co).

According to the configuration 2 of the present disclosure, an etchingrate by a dry etching gas at the time of patterning the phase shift filmcan be increased, so that the film thickness of a resist film can bereduced. This is advantageous in forming a fine pattern of the phaseshift film.

(Configuration 3)

A configuration 3 of the present disclosure is the reflective mask blankaccording to the configuration 1 or 2, in which a protective film isfurther included between the multilayer reflective film and the phaseshift film, the protective film is made of a material containingruthenium (Ru), and the first layer and the second layer are layered inthis order on the protective film.

According to the configuration 3 of the present disclosure, the firstlayer containing tantalum (Ta) and/or chromium (Cr) is arranged betweenthe protective film containing ruthenium (Ru) and the second layer,whereby when the first layer of the phase shift film is etched, it ispossible to use an etching gas to which the protective film containingruthenium (Ru) has resistance.

(Configuration 4)

A configuration 4 of the present disclosure is the reflective mask blankof configuration 1 or 2, in which a protective film is further includedbetween the multilayer reflective film and the phase shift film, theprotective film is made of a material containing silicon (Si) and oxygen(O), and the second layer and the first layer are layered in this orderon the protective film.

According to the configuration 4 of the present disclosure, the secondlayer containing ruthenium (Ru) is arranged on the protective filmcontaining silicon (Si) and oxygen (O), whereby it is possible to use anetching gas to which the protective film has resistance to etch thesecond layer of the phase shift film.

(Configuration 5)

A configuration 5 of the present disclosure is a reflective maskcomprising a phase shift pattern obtained by patterning the phase shiftfilm in the reflective mask blank according to any one of theconfigurations 1 to 4.

According to the configuration 5 of the present disclosure, since thephase shift pattern of the reflective mask can absorb EUV light andreflect part of EUV light with a predetermined phase difference withrespect to an opening (a part where the phase shift pattern is notformed), the reflective mask (an EUV mask) of the present disclosure canbe manufactured by patterning the phase shift film of the reflectivemask blank.

(Configuration 6)

A configuration 6 of the present disclosure is a method of manufacturinga reflective mask, in which the first layer in the reflective mask blankaccording to any one of the configurations 1 to 4 comprises a materialcontaining tantalum (Ta), and a phase shift pattern is formed bypatterning the second layer by a dry etching gas comprising achlorine-based gas and an oxygen gas and then by patterning the firstlayer by a dry etching gas comprising a halogen-based gas comprising nooxygen gas.

The first layer containing tantalum (Ta) can be etched by the dryetching gas including a halogen-based gas including no oxygen gas.Meanwhile, the second layer containing ruthenium (Ru) has resistance tothe dry etching gas including a halogen-based gas including no oxygengas. According to the configuration 6 of the present disclosure, thefirst layer and the second layer are etched by different dry etchinggases, whereby the phase shift film including the first layer and thesecond layer can be patterned finely and highly accurately.

(Configuration 7)

A configuration 7 of the present disclosure is a method of manufacturinga reflective mask, in which the first layer in the reflective mask blankaccording to any one of the configurations 1 to 4 comprises a materialcontaining chromium (Cr), and a phase shift pattern is formed bypatterning the second layer by a dry etching gas comprising an oxygengas and then by patterning the first layer by a dry etching gascomprising a chlorine-based gas comprising no oxygen gas.

The first layer containing chromium (Cr) can be etched by the dryetching gas including a chlorine-based gas including no oxygen gas.Meanwhile, the second layer containing ruthenium (Ru) has resistance tothe dry etching gas including a chlorine-based gas including no oxygengas. According to the configuration 7 of the present disclosure, thefirst layer and the second layer are etched by different dry etchinggases, whereby the phase shift film including the first layer and thesecond layer can be patterned finely and highly accurately.

(Configuration 8)

A configuration 8 of the present disclosure is a method of manufacturinga reflective mask, in which the first layer in the reflective mask blankaccording to any one of the configurations 1 to 4 comprises a materialcontaining chromium (Cr), and a phase shift pattern is formed bypatterning the second layer and the first layer by a dry etching gascomprising a chlorine-based gas and an oxygen gas.

According to the configuration 8 of the present disclosure, the firstlayer containing chromium (Cr) and the second layer containing ruthenium(Ru) are etched by a predetermined one kind of a dry etching gas,whereby a phase shift film including the first layer and the secondlayer can be patterned by a single etching process.

(Configuration 9)

A configuration 9 of the present disclosure is a method of manufacturinga semiconductor device, in which the method includes the reflective maskof the configuration 5 in an exposure apparatus comprising an exposurelight source that emits EUV light, and transferring a transfer patternto a resist film formed on a transferred substrate.

According to the method of manufacturing a semiconductor deviceaccording to the configuration 9 of the present disclosure, a reflectivemask capable of reducing the film thickness of the phase shift film,reducing the shadowing effect, and forming a fine and highly accuratephase shift pattern in a stable cross-sectional shape with smallsidewall roughness can be used for manufacturing a semiconductor device.Thus, a semiconductor device having a fine and highly accurate transferpattern can be manufactured.

According to the reflective mask blank of the present disclosure (thereflective mask manufactured by this reflective mask blank), the filmthickness of the phase shift film can be reduced, the shadowing effectcan be reduced, and the fine and highly accurate phase shift pattern canbe formed in a stable cross-sectional shape with small sidewallroughness. Thus, the reflective mask manufactured by using thereflective mask blank having this structure can form the phase shiftpattern itself finely and highly accurately on the mask and at the sametime prevent a decrease in the accuracy due to shadowing duringtransfer. In addition, by performing EUV lithography using thisreflective mask, it becomes possible to provide a method ofmanufacturing a fine and highly accurate semiconductor device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional diagram of a main part fordescribing a schematic configuration of a reflective mask blank of thepresent disclosure.

FIGS. 2A-2E are step diagrams showing, in schematic cross-sectionaldiagrams, a main part of a step of manufacturing a reflective mask fromthe reflective mask blank.

FIG. 3 is a graph showing a relationship between the film thickness of aphase shift film, relative reflectance with respect to light having awavelength of 13.5 nm, and a phase difference.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be specificallydescribed with reference to the drawings. Note that each of thefollowing embodiments is one mode for embodying the present disclosureand does not limit the present disclosure within the scope thereof. Notethat in the drawings, the same or corresponding parts are denoted by thesame reference signs, and description thereof may be simplified oromitted.

<Structure of Reflective Mask Blank 100 and Method of Manufacturing theSame>

FIG. 1 is a schematic cross-sectional diagram of a main part fordescribing a schematic configuration of a reflective mask blank 100 ofthe present embodiment. As shown in the figure, the reflective maskblank 100 has a mask blank substrate 1 (also simply referred to as“substrate 1”), a multilayer reflective film 2, a protective film 3, anda phase shift film 4 (a lower layer 41 and an upper layer 42) that arelayered in this order. The multilayer reflective film 2 reflects EUVlight that is exposure light formed on a side of a first main surface (afront surface). The protective film 3 is provided to protect themultilayer reflective film 2 and is formed of a material havingresistance to an etchant and a cleaning liquid used when the phase shiftfilm 4 to be described later is patterned. The phase shift film 4absorbs EUV light. In addition, a back side conductive film 5 for anelectrostatic chuck is formed on a side of a second main surface (a backsurface) of the substrate 1.

In the present specification, the expression “having the multilayerreflective film 2 on a main surface of the mask blank substrate 1” meansthat the multilayer reflective film 2 is arranged in contact with thesurface of the mask blank substrate 1, and the expression also includesa meaning of having another film between the mask blank substrate 1 andthe multilayer reflective film 2. The same applies to other films. Forexample, the expression “having a film B on a film A” means that thefilm A and the film B are arranged so as to be in direct contact witheach other, and the expression also includes a meaning of having anotherfilm between the film A and the film B. In addition, in the presentspecification, for example, the expression “the film A is arranged incontact with the surface of the film B” means that the film A and thefilm B are arranged in direct contact with each other without anotherfilm interposed between the film A and the film B.

In the present specification, an expression that the second layer is,for example, “a thin film that includes a material including a metalcontaining ruthenium (Ru) and chromium (Cr)” means that the second layerincludes a thin film including substantially at least a materialcontaining ruthenium (Ru) and chromium (Cr). Meanwhile, an expressionthat the second layer is “a thin film that includes ruthenium (Ru) andchromium (Cr)” may mean that the second layer includes only ruthenium(Ru) and chromium (Cr). In addition, in any case, the expressionsinclude a meaning that the second layer includes an impurity that isinevitably mixed.

Hereinafter, each layer will be described.

<<Substrate 1>>

As the substrate 1, a substrate having a low thermal expansioncoefficient in the range of 0±5 ppb/° C. is preferably used in order toprevent distortion of a phase shift pattern 4 a due to heat duringexposure to EUV light. As the material having a low thermal expansioncoefficient in this range, for example, SiO₂—TiO₂-based glass andmulticomponent glass ceramics can be used.

In view of obtaining at least pattern transfer accuracy and positionaccuracy, the first main surface on a side of the substrate 1 where atransfer pattern (constituted by the phase shift film 4 to be describedlater) is formed has been subjected to a surface treatment so that thefirst main surface has high flatness. In the case of EUV exposure,flatness in an area of 132 mm×132 mm of the main surface on the side ofthe substrate 1 where the transfer pattern is formed is preferably 0.1μm or less, more preferably 0.05 μm or less, and particularly preferably0.03 μm or less. In addition, the second main surface on a side oppositeto the side on which the transfer pattern is formed is a surface to beelectrostatically chucked at the time of setting on an exposureapparatus, and the second main surface has preferably a flatness of 0.1μm or less, more preferably 0.05 μm or less, and particularly preferably0.03 μm or less in an area of 132 mm×132 mm. Note that flatness in anarea of 142 mm×142 mm on a side of the second main surface in thereflective mask blank 100 is preferably 1 μm or less, more preferably0.5 μm or less, and particularly preferably 0.3 μm or less.

In addition, high surface smoothness of the substrate 1 is also anextremely important item. The surface roughness of the first mainsurface of the substrate 1 where the phase shift pattern 4 a fortransfer is formed has preferably a root mean square roughness (RMS) of0.1 nm or less. Note that the surface smoothness can be measured with anatomic force microscope.

Furthermore, the substrate 1 has preferably high rigidity in order toprevent deformation due to film stress of a film (such as the multilayerreflective film 2) formed on the substrate 1. In particular, thesubstrate 1 has preferably a high Young's modulus of 65 GPa or more.

<<Multilayer Reflective Film 2>>

The multilayer reflective film 2 imparts a function that reflects EUVlight in a reflective mask 200, and is a multilayer film in which layerseach including, as a main component, an element having a differentrefractive index are periodically layered.

Generally, as the multilayer reflective film 2, there is used amultilayer film in which a thin film (a high refractive index layer) ofa light element that is a high refractive index material or a compoundof the light element and a thin film (a low refractive index layer) of aheavy element that is a low refractive index material or a compound ofthe heavy element are alternately layered for about 40 to 60 periods.The multilayer film may be formed by counting, as one period, a stack ofa high refractive index layer and a low refractive index layer in whichthe high refractive index layer and the low refractive index layer arelayered in this order from the substrate 1 and by building up aplurality of periods of the stack. In addition, the multilayer film maybe formed by counting, as one period, a stack of a low refractive indexlayer and high refractive index layer in which the low refractive indexlayer and the high refractive index layer are layered in this order fromthe substrate 1 and by building up the stack for a plurality of periods.Note that a layer of the outermost surface of the multilayer reflectivefilm 2, that is, a surface layer of the multilayer reflective film 2 ona side opposite to the substrate 1 is preferably a high refractive indexlayer. In a case where in the multilayer film described above, a stackof a high refractive index layer and a low refractive index layer inwhich the high refractive index layer and the low refractive index layerare layered in this order from the substrate 1 is counted as one periodand the stack is built up for a plurality of periods, the uppermostlayer is a low refractive index layer. In this case, if the lowrefractive index layer constitutes the outermost surface of themultilayer reflective film 2, the low refractive index layer is easilyoxidized and the reflectance of the reflective mask 200 is reduced.Thus, it is preferable to further form a high refractive index layer onthe low refractive index layer that is the uppermost layer to form themultilayer reflective film 2. Meanwhile, in a case where in themultilayer film described above, a stack of a low refractive index layerand a high refractive index layer in which the low refractive indexlayer and the high refractive index layer are layered in this order fromthe substrate 1 is counted as one period and the stack is built up for aplurality of periods, the uppermost layer is a high refractive indexlayer and this stack is good as is.

In the present embodiment, a layer containing silicon (Si) is employedas the high refractive index layer. As a material containing Si, a Sicompound containing Si and boron (B), carbon (C), nitrogen (N), and/oroxygen (O) can be used in addition to Si alone. By using the layercontaining Si as the high refractive index layer, the reflective mask200 for EUV lithography having an excellent reflectance for EUV lightcan be obtained. In addition, in the present embodiment, a glasssubstrate is preferably used as the substrate 1. Si also has excellentadhesion to the glass substrate. In addition, as the low refractiveindex layer, a metal alone selected from molybdenum (Mo), ruthenium(Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof is used. Forexample, as the multilayer reflective film 2 for EUV light having awavelength of 13 nm to 14 nm, a Mo/Si periodic film stack in which a Mofilm and a Si film are alternately layered for about 40 to 60 periods ispreferably used. Note that a high refractive index layer that is theuppermost layer of the multilayer reflective film 2 may be formed usingsilicon (Si), and a silicon oxide layer containing silicon and oxygenmay be formed between the uppermost layer (Si) and the Ru-basedprotective film 3. Thus, mask cleaning resistance can be improved.

The reflectance of such a multilayer reflective film 2 alone is usually65% or more, and the upper limit thereof is usually 73%. Note that thefilm thickness and the period of each constituent layer of themultilayer reflective film 2 need to be appropriately selected accordingto an exposure wavelength and are selected so as to satisfy the Braggreflection law. In the multilayer reflective film 2, there are aplurality of high refractive index layers and a plurality of lowrefractive index layers, but the film thickness does not need to be thesame between the high refractive index layers and between the lowrefractive index layers. In addition, the film thickness of a Si layerof the outermost surface of the multilayer reflective film 2 can beadjusted in a range that does not decrease the reflectance. The filmthickness of Si (a high refractive index layer) of the outermost surfacecan be 3 nm to 10 nm.

A method of forming the multilayer reflective film 2 is publicly knownin this technical field. For example, the multilayer reflective film 2can be formed by forming a film of each layer of the multilayerreflective film 2 by an ion beam sputtering method. In the case of theMo/Si periodic multilayer film described above, first, a Si film havinga thickness of about 4 nm is formed on the substrate 1 using a Si targetby, for example, an ion beam sputtering method. Thereafter, a Mo filmhaving a thickness of about 3 nm is formed using a Mo target. This stackof a Si film and a Mo film is counted as one period and the stack isbuild up for 40 to 60 periods to form the multilayer reflective film 2(the layer of the outermost surface is a Si layer). In addition, whenthe multilayer reflective film 2 is formed, it is preferable to form themultilayer reflective film 2 by supplying krypton (Kr) ion particlesfrom an ion source and performing ion beam sputtering.

<<Protective Film 3>>

The protective film 3 can be formed on the multilayer reflective film 2or in contact with a surface of the multilayer reflective film 2 inorder to protect the multilayer reflective film 2 from dry etching andcleaning in a manufacturing process of the reflective mask 200 to bedescribed later. In addition, the protective film 3 also serves toprotect the multilayer reflective film 2 when a black defect of thephase shift pattern 4 a is repaired using an electron beam (EB). Here,FIG. 1 shows a case where the protective film 3 is one layer, but theprotective film 3 can have a stack of three or more layers. Theprotective film 3 is formed of a material having resistance to theetchant and the cleaning liquid used when the phase shift film 4 ispatterned. The protective film 3 is formed on the multilayer reflectivefilm 2, whereby it is possible to reduce damage to the surface of themultilayer reflective film 2 when the reflective mask 200 (an EUV mask)is manufactured using a substrate with a multilayer reflective film.Thus, a reflectance characteristic of the multilayer reflective film 2with respect to EUV light is improved.

Hereinafter, the case where the protective film 3 is one layer will bedescribed as an example. Note that in a case where the protective film 3includes a plurality of layers, properties of a material of theuppermost layer of the protective film 3 (a layer in contact with thephase shift film 4) become important in relation with the phase shiftfilm 4.

In the reflective mask blank 100 of the present embodiment, as amaterial of the protective film 3, a material having resistance to anetching gas used for the dry etching for patterning the phase shift film4 formed on the protective film 3 can be selected. In a case where thephase shift film 4 is formed of a plurality of layers, the material ofthe protective film 3 in contact with the phase shift film 4 (theuppermost layer of the protective film 3 in a case where the protectivefilm 3 includes a plurality of layers), a material having resistance toan etching gas used for dry etching for patterning the lowermost layerof the phase shift film 4 (a layer in contact with the protective film3) among layers forming the phase shift film 4 can be selected. Thematerial of the protective film 3 is preferably a material with which anetching selection ratio of the lowermost layer of the phase shift film 4to the protective film 3 (an etching rate of the lowermost layer of thephase shift film 4/an etching rate of the protective film 3) is 1.5 ormore and preferably 3 or more.

For example, in a case where the lowermost layer of the phase shift film4 is a thin film that includes a material including a metal containingruthenium (Ru) and at least one or more elements of chromium (Cr),nickel (Ni), and cobalt (Co) (a predetermined Ru-based material) or amaterial including a metal containing ruthenium (Ru) and at least one ormore elements of vanadium (V), niobium (Nb), molybdenum (Mo), tungsten(W), and rhenium (Re) (a predetermined Ru-based material), the lowermostlayer of the phase shift film 4 can be etched by a mixed gas of achlorine-based gas and an oxygen gas or a dry etching gas using anoxygen gas. As the material of the protective film 3 having resistanceto this etching gas, a silicon-based material such as silicon (Si), amaterial containing silicon (Si) and oxygen (O), or a materialcontaining silicon (Si) and nitrogen (N) can be selected. Thus, in acase where the lowermost layer of the phase shift film 4 in contact witha surface of the protective film 3 is a thin film including thepredetermined Ru-based material, the protective film 3 preferablyincludes the silicon-based material described above. The silicon-basedmaterial described above has resistance to the mixed gas of achlorine-based gas and the oxygen gas or the dry etching gas using anoxygen gas, and the resistance increases as the oxygen contentincreases. Thus, the material of the protective film 3 is morepreferably silicon oxide (SiO_(x), 1≤x≤2), more preferably, x is large,and particularly preferably, the material of the protective film 3 isSiO₂.

In addition, in a case where the lowermost layer of the phase shift film4 in contact with the surface of the protective film 3 is a thin filmincluding a material containing tantalum (Ta), the lowermost layer ofthe phase shift film 4 can be etched by dry etching using ahalogen-based gas including no oxygen gas. As a material of theprotective film 3 having resistance to this etching gas, a materialcontaining ruthenium (Ru) as a main component can be selected.

In addition, in a case where the lowermost layer of the phase shift film4 in contact with the surface of the protective film 3 is a thin filmincluding a material containing chromium (Cr), the lowermost layer ofthe phase shift film 4 can be etched by dry etching using a dry etchinggas that is a chlorine-based gas including no oxygen gas or a mixed gasof an oxygen gas and a chlorine-based gas. As a material of theprotective film 3 having resistance to this etching gas, a materialcontaining ruthenium (Ru) as a main component can be selected as in acase where the material containing tantalum (Ta) described above is usedfor the lowermost layer of the phase shift film 4.

The material of the protective film 3 that can be used in a case wherethe lowermost layer of the phase shift film 4 is a material containingtantalum (Ta) or chromium (Cr) is a material containing ruthenium as amain component as described above. As the material containing rutheniumas a main component, a Ru metal alone, a Ru alloy containing Ru and atleast one kind of a metal selected from titanium (Ti), niobium (Nb),molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), lanthanum (La),cobalt (Co), rhenium (Re), and the like, and a material containing a Rumetal or a Ru alloy and nitrogen can specifically be mentioned.

In addition, the material of the protective film 3 can be formed of amaterial including a metal containing ruthenium (Ru) and at least one ormore elements of cobalt (Co), niobium (Nb), molybdenum (Mo), and rhenium(Re), which is the same material as a material of a layer above thelowermost layer of the phase shift film 4 (for example, the upper layer42).

In addition, in a case where the lowermost layer of the phase shift film4 is a material containing tantalum (Ta) or chromium (Cr), theprotective film 3 can be, for example, one in which the lowermost layerand the uppermost layer of the protective film 3 are layers including amaterial containing ruthenium as a main component, and a metal or analloy other than Ru is interposed between the lowermost layer and theuppermost layer.

The Ru content ratio of this Ru alloy is 50 atomic % or more and lessthan 100 atomic %, preferably 80 atomic % or more and less than 100atomic %, and more preferably 95 atomic % or more and less than 100atomic %. In particular, in a case where the Ru content ratio of the Rualloy is 95 atomic % or more and less than 100 atomic %, it is possibleto combine the functions of the protective film 3 such as mask cleaningresistance, an etching stopper function when the phase shift film 4 isetched, and the prevention of a change of the multilayer reflective film2 with time while the diffusion of a constituent element (silicon) ofthe multilayer reflective film 2 into the protective film 3 is reducedand the reflectance for EUV light is sufficiently secured.

In EUV lithography, since there are few substances that are transparentto exposure light, it is not technically easy to apply an EUV pelliclethat prevents foreign matters from adhering to a mask pattern surface.For this reason, pellicle-less operation without using a pellicle hasbeen the mainstream. In addition, in the EUV lithography, exposurecontamination such as carbon film deposition on a mask or oxide filmgrowth due to EUV exposure occurs. Thus, it is necessary to frequentlyclean and remove foreign matters and contamination on an EUV reflectivemask at a stage where the mask is used for manufacturing a semiconductordevice. Therefore, the EUV reflective mask is required to haveextraordinary mask cleaning resistance as compared with a transmissivemask for optical lithography. The reflective mask 200 has the protectivefilm 3, whereby cleaning resistance to the cleaning liquid can beincreased.

The film thickness of the protective film 3 is not particularly limitedas long as the function of protecting the multilayer reflective film 2is fulfilled. From the viewpoint of the reflectance for EUV light, thefilm thickness of the protective film 3 is preferably 1.0 nm to 8.0 nmand more preferably 1.5 nm to 6.0 nm.

As a method of forming the protective film 3, it is possible to adopt afilm forming method similar to a publicly known one without anyparticular limitation. As specific examples, a sputtering method and anion beam sputtering method can be mentioned.

<<Phase Shift Film 4>>

The phase shift film 4 that shifts a phase of EUV light is formed on theprotective film 3. In a part where the phase shift film 4 (the phaseshift pattern 4 a) is formed, part of light is reflected at a level thatdoes not adversely affect pattern transfer while EUV light is absorbedand reduced. Meanwhile, EUV light is reflected from the multilayerreflective film 2 through the protective film 3 at an opening (a partwhere the phase shift film 4 is not present). The reflected light fromthe part where the phase shift film 4 is formed forms a desired phasedifference with respect to the reflected light from the opening. Thephase shift film 4 is formed so that a phase difference between thereflected light from the phase shift film 4 and reflected light from themultilayer reflective film 2 is 160 degrees to 200 degrees. Beams of thelight having reversed phase differences in the neighborhood of 180degrees interfere with each other at a pattern edge portion, whereby theimage contrast of a projected optical image is improved. As the imagecontrast is improved, resolution is increased, and variousexposure-related margins such as an exposure margin and a focus marginincrease. Generally, a measure of the reflectance of the phase shiftfilm 4 for obtaining this phase shift effect is 2% or more in terms ofrelative reflectance, though the measure depends on pattern and exposureconditions. The reflectance of the phase shift film 4 is preferably 6%or more in terms of relative reflectance in order to obtain a sufficientphase shift effect. In addition, in a case where the relativereflectance is high to be 10% or more and more preferably 15% or more,the phase difference can be 130 degrees to 160 degrees or 200 degrees to230 degrees in order to further improve the contrast. Here, the relativereflectance of the phase shift film 4 (the phase shift pattern 4 a) isreflectance for EUV light reflected from the phase shift pattern 4 awhen reflectance for EUV light reflected from the multilayer reflectivefilm 2 (including the multilayer reflective film 2 with the protectivefilm 3) in a part where the phase shift pattern 4 a is not present isassumed to be 100%. Note that in this specification, the relativereflectance may be simply referred to as “reflectance”.

In addition, the absolute reflectance of the phase shift film 4 ispreferably 9% or more in order to obtain a sufficient phase shifteffect. Here, the absolute reflectance of the phase shift film 4 (thephase shift pattern 4 a) means reflectance for EUV light reflected fromthe phase shift film 4 (or the phase shift pattern 4 a) (a ratio ofincident light intensity and reflected light intensity).

The relative reflectance of the phase shift pattern 4 a is preferably 6%to 40% in order to further improve resolution and throughput when asemiconductor device is manufactured. The relative reflectance of thephase shift pattern 4 a is required to be more preferably 6 to 35%,still more preferably 15% to 35%, and still more preferably 15% to 25%.

The absolute reflectance of the phase shift film 4 (or the phase shiftpattern 4 a) is desired to be 4% to 27% and more preferably 10% to 17%in order to further improve the resolution and the throughput when asemiconductor device is manufactured.

The phase shift film 4 of the present embodiment has a first layer and asecond layer. The first layer includes a material containing at leastone or more elements of tantalum (Ta) and chromium (Cr). The secondlayer includes a material including a metal containing ruthenium (Ru)and at least one or more elements of chromium (Cr), nickel (Ni), cobalt(Co), vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W), andrhenium (Re).

The phase shift film 4 of the reflective mask blank 100 of the presentembodiment includes the first layer and the second layer including thepredetermined materials, whereby the phase shift pattern 4 a having arelative reflectance of 6% to 40% can be obtained. The predeterminedmaterials are used for the phase shift film 4 of the reflective maskblank 100 of the present embodiment, whereby an absolute reflectance of4% to 27% can be obtained. In addition, the phase shift film 4 of thereflective mask blank 100 of the present embodiment has thin filmthickness necessary for obtaining a predetermined phase difference (aphase difference between the reflected light from the opening and thereflected light from the phase shift pattern 4 a). Thus, a shadowingeffect generated by the phase shift pattern 4 a can be further reducedin the reflective mask 200. In addition, the reflective mask 200manufactured from the reflective mask blank 100 of the presentembodiment is used, whereby it is possible to improve the throughputwhen a semiconductor device is manufactured.

The first layer of the phase shift film 4 of the reflective mask blank100 of the present embodiment will be described. The first layerincludes a material containing at least one or more elements of tantalum(Ta) and chromium (Cr).

As the material of the first layer containing tantalum (Ta), a materialcontaining tantalum (Ta) and one or more elements selected from oxygen(O), nitrogen (N), carbon (C), boron (B), and hydrogen (H) can bementioned. Among these, the material of the first layer is particularlypreferably a material containing tantalum (Ta) and nitrogen (N). Asspecific examples of such a material, tantalum nitride (TaN), tantalumoxynitride (TaON), tantalum boride nitride (TaBN), and tantalum borideoxynitride (TaBON) can be mentioned.

In a case where the first layer contains Ta and N, the composition rangeof Ta and N (the atomic ratio, Ta:N) is preferably 3:1 to 20:1 and morepreferably 4:1 to 12:1. In addition, the film thickness is preferably 2to 55 nm and more preferably 2 to 30 nm.

As the material of the first layer containing chromium (Cr), a materialcontaining chromium (Cr) and one or more elements selected from oxygen(O), nitrogen (N), carbon (C), boron (B), and hydrogen (H) can bementioned. Among these, the material of the first layer is particularlypreferably a material containing chromium (Cr) and carbon (C). Asspecific examples of such a material, chromium nitride (CrC), chromiumoxynitride (CrOC), chromium carbonitride (CrCN), and chromiumoxycarbonitride (CrOCN) can be mentioned.

In a case where the first layer contains Cr and C, the composition rangeof Cr and C (the atomic ratio, Cr:C) is preferably 5:2 to 20:1 and morepreferably 3:1 to 12:1. In addition, the film thickness is preferably 2to 55 nm and more preferably 2 to 25 nm.

In addition, the ranges of a refractive index n and an extinctioncoefficient k in a case where the phase difference of the phase shiftfilm 4 is 160 degrees to 200 degrees are as follows. In a case where therelative reflectance of the phase shift film 4 is 6% to 40% or theabsolute reflectance thereof is 4% to 27%, the refractive index n of thefirst layer including the material containing at least one or moreelements of tantalum (Ta) and chromium (Cr) for EUV light is preferably0.930 to 0.960 and the extinction coefficient k thereof is preferably0.020 to 0.041. In a case where the relative reflectance is 6% to 35% orthe absolute reflectance is 4% to 23%, the refractive index n of thefirst layer for EUV light is preferably 0.930 to 0.960 and theextinction coefficient k thereof is preferably 0.023 to 0.041. In a casewhere the relative reflectance is 15% to 35% or the absolute reflectanceis 10% to 23%, the refractive index n of the first layer for EUV lightis preferably 0.930 to 0.950, and the extinction coefficient k thereofis preferably 0.023 to 0.033. In a case where the relative reflectanceis 15% to 25% or the absolute reflectance is 10% to 17%, the refractiveindex n of the first layer for EUV light is preferably 0.935 to 0.950,and the extinction coefficient k thereof is preferably 0.026 to 0.033.

In addition, the ranges of the refractive index n and the extinctioncoefficient k in a case where the phase difference of the phase shiftfilm 4 is 130 degrees to 160 degrees are as follows. In a case where therelative reflectance of the phase shift film 4 is 10% to 40% or theabsolute reflectance thereof is 6.7% to 27%, the refractive index n ofthe first layer including the material containing at least one or moreelements of tantalum (Ta) and chromium (Cr) for EUV light is preferably0.930 to 0.960 and the extinction coefficient k thereof is preferably0.025 to 0.046.

In addition, the ranges of the refractive index n and the extinctioncoefficient k in a case where the phase difference of the phase shiftfilm 4 is 200 degrees to 230 degrees are as follows. In a case where therelative reflectance of the phase shift film 4 is 10% to 40% or theabsolute reflectance thereof is 6.7% to 27%, the refractive index n ofthe first layer for EUV light is preferably 0.930 to 0.960 and theextinction coefficient k thereof is preferably 0.015 to 0.036.

The second layer of the phase shift film 4 of the reflective mask blank100 of the present embodiment (hereinafter, may be simply referred to as“predetermined Ru-based material”) will be described. The second layerincludes a material including a metal containing ruthenium (Ru) and atleast one or more elements of chromium (Cr), nickel (Ni), cobalt (Co),vanadium (V), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium(Re).

The refractive index n of Ru is n=0.886 (the extinction coefficientk=0.017), and Ru is preferable as a material for the phase shift film 4having high reflectance. However, a Ru-based compound such as RuO islikely to have a crystallized structure and has poor processingcharacteristics. That is, the crystal grain of a crystallized metal islikely to cause large sidewall roughness when the phase shift pattern 4a is formed. Thus, this may have an adverse effect when thepredetermined phase shift pattern 4 a is formed. Meanwhile, in a casewhere a metal of the material of the phase shift film 4 is amorphous, itis possible to reduce the adverse effect when the phase shift pattern 4a is formed. By adding a predetermined element (X) to Ru, the metal ofthe material of the phase shift film 4 can be made amorphous and theprocessing characteristics can be improved. As the predetermined element(X), at least one or more of Cr, Ni, Co, V, Nb, Mo, W, and Re can beselected.

Note that the refractive index n and the extinction coefficient k of Niare n=0.948 and k=0.073, respectively. In addition, as for Co, n=0.933and k=0.066, and as for Cr, n=0.932 and k=0.039. In addition, therefractive index n and the extinction coefficient k of V are n=0.944 andk=0.025, respectively. The refractive index n and the extinctioncoefficient k of Nb are n=0.933 and k=0.005, respectively. Therefractive index n and the extinction coefficient k of Mo are n=0.923and k=0.007, respectively. The refractive index n and the extinctioncoefficient k of W are n=0.933 and k=0.033, respectively. The refractiveindex n and the extinction coefficient k of Re are n=0.914 and k=0.04,respectively. With binary materials (RuCr, RuNi, and RuCo) obtained byadding the predetermined element (X) to Ru, it is possible to make thefilm thickness of the phase shift film 4 thinner than that in the caseof RuTa that is a conventional material. In addition, since theextinction coefficients k of Ni and Co are each larger than theextinction coefficient k of Cr, when Ni and/or Co is selected as theelement (X), the film thickness of the phase shift film 4 can be madethinner than when Cr is selected.

In addition, the ranges of a refractive index n and an extinctioncoefficient k in a case where the phase difference of the phase shiftfilm 4 is 160 degrees to 200 degrees are as follows. In a case where therelative reflectance of the phase shift film 4 is 6% to 40% or theabsolute reflectance thereof is 4% to 27%, the refractive index n of thesecond layer including the material obtained by adding the predeterminedelement (X) to Ru for EUV light is preferably is 0.860 to 0.950 and theextinction coefficient k thereof is preferably 0.008 to 0.095. In a casewhere the relative reflectance is 6% to 35% or the absolute reflectanceis 4% to 23%, the refractive index n of the second layer for EUV lightis preferably 0.860 to 0.950 and the extinction coefficient k thereof ispreferably 0.008 to 0.095. In a case where the relative reflectance is15% to 35% or the absolute reflectance is 10% to 23%, the refractiveindex n is preferably 0.860 to 0.950 and the extinction coefficient kthereof is preferably 0.008 to 0.050. In a case where the relativereflectance is 15% to 25% or the absolute reflectance is 10% to 17%, therefractive index n of the second layer for EUV light is preferably 0.890to 0.950, and the extinction coefficient k thereof is preferably 0.020to 0.050.

In addition, the ranges of the refractive index n and the extinctioncoefficient k in a case where the phase difference of the phase shiftfilm 4 is 130 degrees to 160 degrees are as follows. In a case where therelative reflectance of the phase shift film 4 is 10% to 40% or theabsolute reflectance thereof is 6.7% to 27%, the refractive index n ofthe second layer including the material obtained by adding thepredetermined element (X) to Ru for EUV light is preferably 0.860 to0.950 and the extinction coefficient k thereof is preferably 0.009 to0.095. In a case where the relative reflectance is 15% to 35% or theabsolute reflectance is 10% to 23%, the refractive index n of the secondlayer for EUV light is preferably 0.860 to 0.950 and the extinctioncoefficient k thereof is preferably 0.01 to 0.073.

In addition, the ranges of the refractive index n and the extinctioncoefficient k in a case where the phase difference of the phase shiftfilm 4 is 200 degrees to 230 degrees are as follows. In a case where therelative reflectance of the phase shift film 4 is 10% to 40% or theabsolute reflectance thereof is 6.7% to 27%, the refractive index n ofthe second layer for EUV light is preferably 0.860 to 0.940 and theextinction coefficient k thereof is preferably 0.008 to 0.057. In a casewhere the relative reflectance is 15% to 35% or the absolute reflectanceis 10% to 23%, the refractive index n of the second layer for EUV lightis preferably 0.860 to 0.939 and the extinction coefficient k thereof ispreferably 0.009 to 0.045.

The phase difference and the reflectance of the phase shift film 4 canbe adjusted by changing the refractive index n, the extinctioncoefficient k, the film thickness of the first layer and the filmthickness of the second layer. The film thickness of the first layer ispreferably 55 nm or less and more preferably 30 nm or less. The filmthickness of the first layer is preferably 2 nm or more. In addition,the film thickness of the second layer is preferably 50 nm or less andmore preferably 35 nm or less. The film thickness of the second layer ispreferably 5 nm or more and more preferably 15 nm or more. The filmthickness of the phase shift film 4 (total film thickness of the firstlayer and the second layer) is preferably 60 nm or less, more preferably50 nm or less, and still more preferably 40 nm or less. The filmthickness of the phase shift film 4 is preferably 25 nm or more. Notethat in a case where the protective film 3 is included, the phasedifference and the reflectance of the phase shift film 4 can also beadjusted in consideration of the refractive index n, the extinctioncoefficient k, and the film thickness of the protective film 3.

The binary materials (RuCr, RuNi, and RuCo) obtained by adding thepredetermined element (X) to Ru have better processing characteristicsthan those of RuTa that is a conventional material. When Ta is oxidized,it is difficult to etch by a chlorine-based gas and an oxygen gas. Inparticular, since RuCr can be easily etched by a mixed gas of achlorine-based gas and an oxygen gas, RuCr is excellent in processingcharacteristics. In addition, in a case where the material of the firstlayer contains Cr, the first layer and the second layer can be etched bythe same dry etching gas.

The binary materials (RuCr, RuNi, and RuCo) obtained by adding thepredetermined element (X) to Ru have an amorphous structure and can beeasily etched by a mixed gas of a chlorine-based gas and an oxygen gas.In addition, these materials can be etched by an oxygen gas. The same isthought to apply to ternary materials (RuCrNi, RuCrCo, and RuNiCo) and aquaternary material (RuCrNiCo).

In addition to the binary materials described above, binary materials(RuV, RuNb, RuMo, RuW, and RuRe) obtained by adding V, Nb, Mo, W or Reto Ru have better workability than that of RuTa that is a conventionalmaterial. RuW and RuMo are particularly excellent in processingcharacteristics as with RuCr.

In addition, the binary materials (RuV, RuNb, RuMo, RuW, and RuRe)obtained by adding the predetermined element (X) to Ru have an amorphousstructure and can be easily etched by a mixed gas of a chlorine-basedgas and an oxygen gas. In addition, these materials can be etched by anoxygen gas. The same is thought to apply to ternary materials andquaternary materials.

Next, the mixing ratio of Ru and the predetermined element (X) will bedescribed regarding the predetermined Ru-based material.

The relative reflectance and absolute reflectance of the predeterminedRu-based material increase as Ru content increases. In addition,reflected light of the phase shift film 4 is light generated bysuperposition of surface reflected light from the surface of the phaseshift film 4 and back surface reflected light at a back surface of thephase shift film 4 (an interface between the phase shift film 4 and theprotective film 3 or the multilayer reflective film 2) after passingthrough the phase shift film 4. Thus, the intensity of the reflectedlight of the phase shift film 4 has a periodic structure depending onthe film thickness of the phase shift film 4. As a result, thereflectance and the phase difference of the phase shift film 4 also showa periodic structure depending on the film thickness, as shown as anexample in FIG. 3. Note that FIG. 3 is a graph showing a relationshipbetween the film thickness of the phase shift film 4, the relativereflectance with respect to EUV light, and the phase difference when thefilm thickness of the lower layer 41 (a TaN film) is fixed to 15.5 nmand the film thickness of the upper layer 42 (a RuCr film) is changed ina case where the phase shift film 4 includes two layers, that is, thelower layer 41 that is the TaN film and the upper layer 42 that is theRuCr film, and the atomic ratio of Ru and Cr in the RuCr film isRu:Cr=90:10. The refractive index n and the extinction coefficient k ofthe material of the phase shift film 4 affect the periodic structure.Meanwhile, the reflected light from the phase shift pattern 4 a needs tohave a predetermined phase difference (for example, a phase differenceof 180 degrees) with respect to the reflected light from the opening. Incomprehensive consideration of the above, a relationship between therelative reflectance of the phase shift film 4, and the composition andthe film thickness of the predetermined Ru-based material was studied.As a result, regarding the composition and the film thickness of thepredetermined Ru-based material, preferable ranges can be shownaccording to the relative reflectance of the phase shift film 4, asdescribed below. As shown in FIG. 3, in a case where the lower layer 41of the phase shift film 4 is the TaN film with a film thickness of 15.5nm and the upper layer 42 is the RuCr film (Ru:Cr=90:10), the filmthickness of the RuCr film is 22.8 nm (the film thickness of the phaseshift film 4 is 38.3 nm), the relative reflectance with respect to themultilayer reflective film (with a protective film) is 20.1% (theabsolute reflectance is 13.4%), and the phase difference isapproximately 180 degrees.

Specifically, the following describes a relationship between thecomposition (the atomic ratio) of the predetermined Ru-based materialand the film thickness in a case where when the phase shift film 4includes the two layers, that is, the first layer and the second layer,and the first layer of the phase shift film 4 includes the materialcontaining at least one or more elements of tantalum (Ta) and chromium(Cr), the relative reflectance of the second layer material is 6% to40%.

That is, in a case where the material of the second layer contains Ruand Cr, the composition range (the atomic ratio) of Ru and Cr ispreferably Ru:Cr=40:1 to 1:20 and more preferably 40:1 to 3:7. Inaddition, the film thickness is preferably 5 to 50 nm and morepreferably 15 to 35 nm.

In a case where the material of the second layer contains Ru and Ni, thecomposition range (the atomic ratio) of Ru and Ni is preferablyRu:Ni=40:1 to 1:6 and more preferably 40:1 to 1:1. In addition, the filmthickness is preferably 5 to 45 nm and more preferably 12 to 33 nm.

In a case where the material of the second layer contains Ru and Co, thecomposition range (the atomic ratio) of Ru and Co is preferablyRu:Co=40:1 to 1:7 and more preferably 40:1 to 2:3. In addition, the filmthickness is preferably 5 to 40 nm and more preferably 10 to 30 nm.

In a case where the material of the second layer contains Ru and V, thecomposition range (the atomic ratio) of Ru and V is preferably Ru:V=40:1to 1:20 and more preferably 40:1 to 2:7. In addition, the film thicknessis preferably 5 to 60 nm and more preferably 16 to 50 nm.

In a case where the material of the second layer contains Ru and Nb, thecomposition range (the atomic ratio) of Ru and Nb is preferablyRu:Nb=40:1 to 5: 1 and more preferably 40:1 to 9:1. In addition, thefilm thickness is preferably 5 to 33 nm and more preferably 16 to 33 nm.

In a case where the material of the second layer contains Ru and Mo, thecomposition range (the atomic ratio) of Ru and Mo is preferablyRu:Mo=40:1 to 4:1 and more preferably 40:1 to 9:1. In addition, the filmthickness is preferably 5 to 33 nm and more preferably 15 to 33 nm.

In a case where the material of the second layer contains Ru and W, thecomposition range (the atomic ratio) of Ru and W is preferably Ru:W=40:1to 1:20 and more preferably 40:1 to 17:33. In addition, the filmthickness is preferably 5 to 50 nm and more preferably 16 to 40 nm.

In a case where the material of the second layer contains Ru and Re, thecomposition range (the atomic ratio) of Ru and Re is preferablyRu:Re=40:1 to 1:20 and more preferably 40:1 to 9:16. In addition, thefilm thickness is preferably 5 to 38 nm and more preferably 16 to 33 nm.

As described above, the composition ratios of Ru to Cr, Ni, Co, V, Nb,Mo, W, and Re are in the predetermined ranges, whereby it is possible toobtain the second layer for obtaining the phase shift film 4 having highreflectance and the predetermined phase difference at thin filmthickness.

In the above description, the predetermined Ru-based binary materialshave been mainly described, but the ternary materials (RuCrNi, RuCrCo,RuNiCo, and RuCrW) and the quaternary materials (RuCrNiCo and RuCrCoW)also have properties similar to those of the predetermined Ru-basedbinary materials. Thus, the ternary or quaternary material can be usedas the predetermined Ru-based material.

The predetermined Ru-based material can include Ru and at least one ormore elements of Cr, Ni, Co, V, Nb, Mo, W, and Re, and further, otherelements, in a range that does not significantly affect the refractiveindex and the extinction coefficient. The predetermined Ru-basedmaterial can include an element, for example, nitrogen (N), oxygen (O),carbon (C), or boron (B). For example, the addition of nitrogen (N) tothe predetermined Ru-based material can reduce the oxidation of thephase shift film 4, so that the properties of the phase shift film 4 canbe stabilized. In addition, in a case where nitrogen (N) is added to thepredetermined Ru-based material, a crystalline state can be easilychanged into an amorphous state regardless of the film formingconditions of sputtering. In this case, nitrogen content is preferably 1atomic % or more and more preferably 3 atomic % or more. In addition,the nitrogen content is preferably 10 atomic % or less. Oxygen (O),carbon (C), boron (B), and the like can also be added to the material ofthe phase shift film 4 in a range that does not significantly affect therefractive index and the extinction coefficient for stabilization of thephase shift film 4 and the like. In a case where the material of thephase shift film 4 contains Ru and at least one or more elements of Cr,Ni, Co, V, Nb, Mo, W, and Re, and other elements, the content of theother elements described above is preferably 10 atomic % or less andmore preferably 5 atomic % or less.

The phase shift film 4 including the predetermined Ru-based materialdescribed above can be formed by a known method such as a magnetronsputtering method including a direct-current (DC) sputtering method anda radio-frequency (RF) sputtering method. In addition, an alloy targetof Ru and at least one or more elements of Cr, Ni, Co, V, Nb, Mo, W, andRe can be used as a target.

In addition, a Ru target, a Cr target, a Ni target, a Co target, a Vtarget, a Nb target, a Mo target, a W target and/or a Re target can beused as a target to form a film by co-sputtering. The co-sputtering hasan advantage that the composition ratio of metal elements can be easilyadjusted, but the crystalline state of the film may easily turn into acolumnar structure state as compared with the alloy target. Thecrystalline state can be changed into an amorphous state by forming thefilm so as to include nitrogen (N) therein during sputtering.

In this specification, in a case where the phase shift film 4 includestwo layers, a layer in contact with the multilayer reflective film 2 orthe protective film 3 is referred to as the lower layer 41, and a layerarranged on the surface of the phase shift film 4 on a side opposite tothe multilayer reflective film 2 or the protective film 3 is referred toas the upper layer 42. In a case where the phase shift film 4 includesthree or more layers, generally, the lower layer 41 is arranged at anyposition on a side that is away from the upper layer 42 and on which themultilayer reflective film 2 or the protective film 3 is present. Notethat the lower layer 41 can be the lowermost layer of the phase shiftfilm 4 (a layer in contact with the multilayer reflective film 2 or theprotective film 3 among layers forming the phase shift film 4), and theupper layer 42 can be the uppermost layer of the phase shift film 4 (alayer farthest from the lowermost layer among layers forming the phaseshift film 4). In the following description, each of the first layer andthe second layer is either the upper layer 42 or the lower layer 41.That is, in a case where the first layer including the predeterminedmaterial is the upper layer 42, the second layer including thepredetermined material is the lower layer 41, and in a case where thefirst layer including the predetermined material is the lower layer 41,the second layer including the predetermined material is the upper layer42.

The phase shift film 4 can include only the two layers, that is, thefirst layer and the second layer described above. In addition, the phaseshift film 4 can include a film other than the first layer and thesecond layer. In the present embodiment, the phase shift film 4preferably includes only the two layers, that is, the first layer andthe second layer described above. In a case where the phase shift film 4includes only the two layers, that is, the first layer and the secondlayer, the number of steps in manufacturing the mask blank can bereduced, so that the production efficiency is improved.

In addition, in a case where the phase shift film 4 includes two or morelayers, the film thickness is adjusted without changing the compositionof either one of the first layer and the second layer or the compositionof the first layer and the second layer, whereby the reflectance and thephase difference can be changed.

In a case where the phase shift film 4 includes three or more layers,the phase shift film 4 can have a stack of three or more first layersand second layers alternately layered. The film thickness of the firstlayer and the second layer is adjusted, whereby it is possible toimprove the stability of the phase difference and the reflectance withrespect to film thickness variations. In addition, the uppermost layerof the phase shift film 4 is the second layer, whereby the cleaningresistance can be improved.

The phase shift film 4 can include three or more layers, as describedabove. However, for ease of description, the arrangement of the firstlayer and the second layer will be described by taking, as an example, acase where the phase shift film 4 includes the two layers, that is, thefirst layer and the second layer. In addition, in the following example,a case where the reflective mask blank 100 has the protective film 3will be described. As described below, it is preferable to appropriatelyselect the type of the material of the protective film 3 and arrange thefirst layer and the second layer in consideration of the type of thematerial of the protective film 3 and which of the first layer and thesecond layer is the lower layer 41. This is because the type of dryetching gas that can be used for dry etching and the type of dry etchinggas having resistance to dry etching differ depending on the type ofmaterial.

Hereinafter, first, the etching characteristics of the first layer, thesecond layer, and the protective film 3 will be described.

In a case where the first layer is the material containing tantalum(Ta), the first layer can be patterned by the dry etching gas includinga halogen-based gas including no oxygen gas.

In a case where the first layer is the material containing chromium(Cr), the first layer can be patterned by a chlorine-based dry etchinggas. The chlorine-based dry etching gas can include an oxygen gas or maynot include an oxygen gas.

The second layer including the predetermined Ru-based material can bepatterned by a dry etching gas including oxygen. As the dry etching gas,for example, a gas of an oxygen alone or a gas including an oxygen gasand a chlorine-based gas can be used.

In a case where the material of the protective film 3 is the materialcontaining silicon (Si), the material containing silicon (Si) and oxygen(O), or the material containing silicon (Si) and nitrogen (N), theprotective film 3 has resistance to dry etching using a mixed gas of achlorine-based gas and an oxygen gas or a dry etching gas using anoxygen gas. Note that this dry etching gas can etch the second layerincluding the predetermined Ru-based material.

In a case where the material of the protective film 3 is the materialcontaining ruthenium (Ru) as a main component, the protective film 3 hasresistance to dry etching using a halogen-based gas including no oxygengas. Note that the dry etching gas can etch the first layer containingtantalum (Ta).

In a case where the material of the protective film 3 is the materialcontaining ruthenium (Ru) as a main component, the protective film 3 hasresistance to dry etching using a dry etching gas including achlorine-based gas including no oxygen gas or a dry etching gasincluding a chlorine-based gas including a reduced oxygen gas. This dryetching gas can etch the first layer containing chromium (Cr).

From the etching characteristics of the first layer, the second layer,and the protective film 3 described above, the type of the material ofthe protective film 3 and the arrangement of the first layer and thesecond layer are preferably as follows.

In a case where the protective film 3 includes the material containingruthenium (Ru), the first layer and the second layer are preferablylayered in this order on the protective film 3. The first layercontaining tantalum (Ta) and/or chromium (Cr) is arranged between theprotective film 3 containing ruthenium (Ru) and the second layer,whereby an etching gas having resistance to the protective film 3containing ruthenium (Ru) can be used when the first layer of the phaseshift film 4 is etched.

In a case where the protective film 3 is the silicon-based materialincluding the material containing silicon (Si) and oxygen (O) or thematerial containing silicon (Si) and nitrogen (N), the second layer andthe first layer are preferably layered in this order on the protectivefilm 3. The second layer containing ruthenium (Ru) is arranged on theprotective film 3 including the silicon-based material, whereby anetching gas having resistance to the protective film 3 including thesilicon-based material can be used when the second layer containingruthenium (Ru) of the phase shift film 4 is etched.

In a case where the first layer of the phase shift film 4 is thematerial containing tantalum (Ta), the first layer can be patterned bythe dry etching gas including a halogen-based gas including no oxygengas. In addition, the second layer can be patterned by a dry etching gasincluding a chlorine-based gas and an oxygen gas. This is because thematerial of the first layer containing tantalum (Ta) has resistance tothe dry etching gas including a chlorine-based gas and an oxygen gas,and the material of the second layer has resistance to a dry etching gasincluding no oxygen gas. In this case, the material of the protectivefilm 3 needs to be appropriately selected, depending on which of thefirst layer and the second layer is in contact with the protective film3 (which of the first layer and the second layer is the lower layer 41).That is, in a case where the first layer is the lower layer 41, thematerial containing ruthenium (Ru) as a main component can be used asthe protective film 3. In addition, in a case where the second layer isthe lower layer 41, the silicon-based material, particularly thematerial containing silicon (Si) and oxygen (O) can be used as theprotective film 3.

In a case where the first layer of the phase shift film 4 is thematerial containing chromium (Cr), the second layer can be patterned bya dry etching gas including an oxygen gas, and the first layer can bepatterned by a dry etching gas including a chlorine-based gas includingno oxygen gas. In this case, the material of the protective film 3 needsto be appropriately selected, depending on which of the first layer andthe second layer is in contact with the protective film 3 (which of thefirst layer and the second layer is the lower layer 41). That is, in acase where the first layer is the lower layer 41, the materialcontaining ruthenium (Ru) as a main component can be used as theprotective film 3. In addition, in a case where the second layer is thelower layer 41, the silicon-based material, particularly the materialcontaining silicon (Si) and oxygen (O) can be used as the protectivefilm 3. The first layer containing chromium (Cr) and the second layercontaining ruthenium (Ru) are etched by different dry etching gases,whereby the phase shift film 4 can be patterned finely and highlyaccurately.

In a case where the first layer of the phase shift film 4 is thematerial containing chromium (Cr), the second layer and the first layercan be patterned by a dry etching gas including a chlorine-based gas andan oxygen gas. In this case, both of the first layer and the secondlayer can be etched by a single etching step. Thus, the phase shift film4 can be patterned at appropriate throughput. In this case, the flowrate ratio of the chlorine-based gas to the oxygen-based gas ispreferably 3:1 to 10:1.

As the protective film 3, it is preferable to use a silicon-basedmaterial having resistance to a dry etching gas of a mixed gas of achlorine-based gas and an oxygen gas, particularly a material containingsilicon (Si) and oxygen (O). As the protective film 3, the materialcontaining ruthenium (Ru) as a main component can be used, but in thiscase, it is necessary to reduce the oxygen gas in the mixed gas so thatthe protective film 3 is not etched by the dry etching gas. Thus, inthat case, the flow rate ratio of the chlorine-based gas to the oxygengas is preferably 10:1 to 40:1.

Note that even if the material of the protective film 3 is a materialother than the materials described above, it is possible to select amaterial with which an etching selection ratio of the phase shift film 4to the protective film 3 in the dry etching using a predetermined dryetching gas (an etching rate of the phase shift film 4/an etching rateof the protective film 3) is 1.5 or more and preferably 3 or more.

As the halogen-based gas used in the dry etching described above, afluorine-based gas and/or a chlorine-based gas can be used. As thefluorine-based gas, CF₄, CHF₃, C₂F₆, C₃F₆, C₄F₆, C₄F₈, CH₂F₂, CH₃F,C₃F₈, SF₆, F₂, and the like can be used. As the chlorine-based gas, Cl₂,SiCl₄, CHCl₃, CCl₄, BCl₃, and the like can be used. In addition, a mixedgas including a fluorine-based gas and/or a chlorine-based gas and O₂ ina predetermined ratio can be used, if necessary. These etching gases canfurther include an inert gas such as He and/or Ar, if necessary.

Since EUV light has a short wavelength, the phase difference and thereflectance tend to depend greatly on the film thickness. Thus, thestability of the phase difference and the reflectance with respect tothe film thickness variations of the phase shift film 4 is required.However, as shown in FIG. 3, the phase difference and the reflectanceeach show a vibrating structure with respect to the film thickness ofthe phase shift film 4. Since the vibrating structures of the phasedifference and the reflectance are different, it is difficult to havethe film thickness at which the phase difference and the reflectance arestabilized at the same time.

Therefore, even if the film thickness of the phase shift film 4 slightlyvaries with respect to a design value (for example, in the range of±0.5% with respect to design film thickness), as for the phasedifference, variations in the phase difference between the surfaces aredesired to be in the range of the predetermined phase difference±2degrees (for example, in a case where the phase difference is 180degrees, in the range of 180 degrees±2 degrees), and as for thereflectance, variations in the reflectance between the surfaces aredesired to be in the range of the predetermined reflectance±0.2% (forexample, in a case where the relative reflectance is 6%, in the range of6%±0.2%).

The upper layer 42 of the phase shift film 4 may be thinned at the timeof removing and/or cleaning a resist film and an etching mask film, andtherefore in a case where focus is on reducing variations in the phasedifference of the phase shift film 4, it is preferable to arrange, thesecond layer having a large contribution to the phase difference as thelower layer 41.

In addition, in a case where the phase shift film 4 is formed byincluding the uppermost layer, the upper layer 42, and the lower layer41, the reflected light of EUV light from the surface of the uppermostlayer is reduced, whereby it is possible to smooth the vibratingstructure with respect to the film thickness variations and obtain astable phase difference and reflectance. As a material of such anuppermost layer, a silicon compound or a tantalum compound having arefractive index larger than that of the upper layer 42 of the phaseshift film 4 is preferable. As the silicon compound, a materialcontaining Si and at least one element selected from N, O, C and H, andpreferably SiO₂, SiON, and Si₃N₄ can be mentioned. As the tantalumcompound, a material containing Ta and at least one element selectedfrom N, O, C, H, and B can be mentioned, and a material containing Taand O can preferably be mentioned. The film thickness of the uppermostlayer is preferably 10 nm or less, more preferably 1 to 6 nm, and stillmore preferably 3 to 5 nm. In a case where the upper layer 42 is a RuCrfilm, the uppermost layer can be, for example, a SiO₂ film or a Ta₂O₅film.

As described above, the phase shift film 4 is formed to be a multilayerfilm, whereby various functions can be added to each layer.

The crystal structure of the phase shift film 4 of the reflective maskblank 100 of the present embodiment is preferably amorphous. Since thecrystal structure of the phase shift film 4 is amorphous, it is possibleto reduce adverse effects caused by the crystal gain of a metal or thelike when the phase shift pattern 4 a is formed. Thus, the crystalstructure of the phase shift film 4 is made amorphous, whereby it ispossible to increase the etching rate when the phase shift film 4 isetched, improve a pattern shape, and improve the processingcharacteristics.

In addition, in a case where focus is on improving the cross-sectionalshape of the phase shift pattern 4 a, it is preferable to arrange, thefirst layer having a higher etching rate than that of the second layeras the lower layer 41.

<<Etching Mask Film>>

The etching mask film can be formed on the phase shift film 4 or incontact with the surface of the phase shift film 4. As a material of theetching mask film, a material with which an etching selection ratio ofthe phase shift film 4 to the etching mask film is high is used. Here,the expression “an etching selection ratio of B to A” means a ratio ofan etching rate of A that is a layer not desired to be etched (a layerto become a mask) to an etching rate of B that is a layer desired to beetched. Specifically, the expression “an etching selection ratio of B toA” is specified by the equation “an etching selection ratio of B to A=anetching rate of B/an etching rate of A”. In addition, the expression“high selection ratio” means that a value of the selection ratio definedabove is large as compared with that of an object for comparison. Theetching selection ratio of the phase shift film 4 to the etching maskfilm is preferably 1.5 or more, and more preferably 3 or more.

In a case where the second layer (the predetermined ruthenium (Ru)-basedmaterial) is the uppermost layer of the phase shift film 4, the secondlayer can be etched by dry etching using a chlorine-based gas includingoxygen or an oxygen gas. As a material of the etching mask film withwhich the etching selection ratio of the phase shift film 4 includingthe predetermined ruthenium (Ru)-based material with respect to theetching mask film is high, a silicon (Si)-based material or a tantalum(Ta)-based material can be used.

In a case where the uppermost layer of the phase shift film 4 is thesecond layer, the silicon (Si)-based material that can be used for theetching mask film is silicon or a silicon compound material. As thesilicon compound, a material containing Si and at least one elementselected from N, O, C, and H and a silicon-based material such asmetallic silicon (metal silicide) including silicon or a siliconcompound, or a metal silicon compound (a metal silicide compound) can bementioned. As the metal silicon compound, a material including a metal,Si, and at least one element selected from N, O, C, and H can bementioned.

As the tantalum (Ta)-based material that can be used as the etching maskfilm in a case where the uppermost layer of the phase shift film 4 isthe second layer, a material containing tantalum (Ta) and one or moreelement selected from oxygen (O), nitrogen (N), carbon (C), boron (B),and hydrogen (H) can be mentioned. Among these, it is particularlypreferable to use a material containing tantalum (Ta) and oxygen (O) asthe material of the etching mask film. As specific examples of such amaterial, tantalum oxide (TaO), tantalum oxynitride (TaON), tantalumboride oxide (TaBO), and tantalum boride oxynitride (TaBON) can bementioned.

In a case where the first layer is the uppermost layer of the phaseshift film 4 and the first layer is the material containing tantalum(Ta), as a material of the etching mask film with which an etchingselection ratio of the first layer to the etching mask film is high, achromium (Cr)-based material and a silicon (Si)-based material can bementioned. As the chromium (Cr)-based material, a material of chromiumor a chromium compound can be used. As the chromium compound, a materialcontaining Cr and at least one element selected from N, O, C, and H canbe mentioned. As the silicon compound, a material similar to thatdescribed in the case where the second layer described above is theuppermost layer of the phase shift film 4 can be used.

In a case where the first layer is the uppermost layer of the phaseshift film 4 and the first layer is the material containing chromium(Cr), as a material of the etching mask film with which the etchingselection ratio of the first layer to the etching mask film is high, asilicon (Si)-based material and a tantalum (Ta)-based material can bementioned. As the silicon (Si)-based material and the tantalum(Ta)-based material, materials similar to those described in the casewhere the second layer described above is the uppermost layer of thephase shift film 4 can be used.

The film thickness of the etching mask film is desirably 3 nm or morefrom the viewpoint of obtaining a function as an etching mask foraccurately forming the transfer pattern on the phase shift film 4. Inaddition, the film thickness of the etching mask film is desirably 15 nmor less from the viewpoint of reducing the film thickness of a resistfilm 11.

<<Back Side Conductive Film 5>>

The back side conductive film 5 for an electrostatic chuck is generallyformed on a side of the second main surface (the back surface) of thesubstrate 1 (a side opposite to a surface on which the multilayerreflective film 2 is formed). An electrical characteristic (sheetresistance) required of the back side conductive film 5 for anelectrostatic chuck is usually 100Ω/□ (Ω/square) or less. By a method offorming the back side conductive film 5, it is possible to form the backside conductive film 5 using, for example, a magnetron sputtering methodor an ion beam sputtering method using a target of a metal alone such aschromium, tantalum, and the like or an alloy thereof

A material containing chromium (Cr) for the back side conductive film 5is preferably a Cr compound containing Cr and at least one selected fromboron, nitrogen, oxygen, and carbon. As the Cr compound, for example,CrN, CrON, CrCN, CrCO, CrCON, CrBN, CrBON, CrBCN, and CrBOCN can bementioned.

As a material containing tantalum (Ta) for the back side conductive film5, it is preferable to use Ta (tantalum), an alloy containing Ta, or aTa compound containing either of Ta or an alloy containing Ta and atleast one from boron, nitrogen, oxygen, and carbon. As the Ta compound,TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO,TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, and TaSiCON can bementioned.

As a material containing tantalum (Ta) or chromium (Cr), an amount ofnitrogen (N) present in the surface layer thereof is preferably small.Specifically, nitrogen content in the surface layer of the back sideconductive film 5 including the material containing tantalum (Ta) orchromium (Cr) is preferably less than 5 atomic %, and more preferably,the surface does not substantially contain nitrogen. This is because inthe back side conductive film 5 including the material containingtantalum (Ta) or chromium (Cr), the lower the nitrogen content in thesurface layer is, the higher wear resistance is.

The back side conductive film 5 is preferably including a materialcontaining tantalum and boron. The back side conductive film 5 includesthe material containing tantalum and boron, whereby the back sideconductive film 5 having wear resistance and chemical resistance can beobtained. In a case where the back side conductive film 5 containstantalum (Ta) and boron (B), B content is preferably 5 to 30 atomic %.The ratio of Ta and B (Ta:B) in a sputtering target used for forming theback side conductive film 5 is preferably from 95:5 to 70:30.

The thickness of the back side conductive film 5 is not particularlylimited as long as a function as being for an electrostatic chuck isfulfilled. The thickness of the back side conductive film 5 is usually10 nm to 200 nm. In addition, the back side conductive film 5 also has afunction of adjusting stress on the side of the second main surface ofthe mask blank 100, and is adjusted so that a balance with stress fromvarious films formed on the side of the first main surface is kept andthe flat reflective mask blank 100 can be obtained.

<Reflective Mask 200 and Manufacturing Method of the Same>

The present embodiment is the reflective mask 200 having the phase shiftpattern 4 a in which the phase shift film 4 of the reflective mask blank100 described above is partnered. The phase shift pattern 4 a can beformed by patterning the phase shift film 4 of the reflective mask blank100 described above, the phase shift film 4, by a predetermined dryetching gas (for example, a dry etching gas including a chlorine-basedgas and an oxygen gas). The phase shift pattern 4 a of the reflectivemask 200 can absorb EUV light and reflect part of the EUV light at apredetermined phase difference (for example, 180 degrees) with respectto an opening (a part where the phase shift pattern is not formed). Topattern the phase shift film 4, an etching mask film may be provided onthe phase shift film 4, if necessary, an etching mask film pattern maybe used as a mask, and the phase shift film 4 may be subjected to dryetching to form the phase shift pattern 4 a.

A method of manufacturing the reflective mask 200 using the reflectivemask blank 100 of the present embodiment will be described. Here, anoutline description will be only given, and a detailed description willbe given later in Examples with reference to the drawings.

The reflective mask blank 100 is prepared, and the resist film 11 isformed on the phase shift film 4 on the first main surface of thereflective mask blank 100 (this step is not necessary in a case wherethe resist film 11 is provided as the reflective mask blank 100). Next,a desired pattern is drawn (exposed) on the resist film 11 and furtherdeveloped and rinsed, whereby a predetermined resist pattern 11 a isformed.

In the case of the reflective mask blank 100, this resist pattern 11 ais used as a mask, the phase shift film 4 (the upper layer 42 and thelower layer 41) is each etched using a predetermined etching gas to formthe phase shift pattern 4 a, and the resist pattern 11 a is removed byashing, a resist stripping solution, or the like, whereby the phaseshift pattern 4 a is formed. Finally, wet cleaning is performed using anacidic and/or alkaline aqueous solution.

Here, as the etching gas for the phase shift film 4 (the upper layer 42and the lower layer 41), it is necessary to select an appropriateetching gas as described above, depending on the material used. Thematerials of the phase shift film 4 (the upper layer 42 and the lowerlayer 41), the protective film 3, and the etching gases correspondingthereto are appropriately selected, whereby it is possible to preventroughening of the surface of the protective film 3 when the phase shiftfilm 4 is etched.

Through the above steps, the reflective mask 200 having a fine andhighly accurate pattern having a small shadowing effect and small wallroughness can be obtained.

<Method of Manufacturing Semiconductor Device>

The present embodiment is a method of manufacturing a semiconductordevice. The semiconductor device can be manufactured by setting thereflective mask 200 of the present embodiment in an exposure apparatushaving an EUV light exposure light source and then by transferring atransfer pattern to a resist film formed on a transfer-receivingsubstrate.

Specifically, by performing EUV exposure using the reflective mask 200described above of the present embodiment, a desired transfer patternbased on a phase shift pattern 4 a on the reflective mask 200 can beformed on a semiconductor substrate while a decrease in accuracy of atransfer dimension due to a shadowing effect can be suppressed. Inaddition, since the phase shift pattern 4 a is a fine and highlyaccurate pattern with small sidewall roughness, a desired pattern can beformed on the semiconductor substrate with high dimensional accuracy.With various steps such as etching of a film to be processed, formationof an insulating film and a conductive film, introduction of a dopant,and annealing in addition to this lithography step, it is possible tomanufacture a semiconductor device on which a desired electronic circuitis formed.

More specifically, an EUV exposure apparatus includes a laser plasmalight source that generates EUV light, an illumination optical system, amask stage system, a reduction projection optical system, a wafer stagesystem, and vacuum equipment. The light source is provided with a debristrap function, a cut filter that cuts light having a long wavelengthother than exposure light, a vacuum differential pumping facility, andthe like. The illumination optical system and the reduction projectionoptical system each include a reflection mirror. The reflective mask 200for EUV exposure is electrostatically attracted by the back sideconductive film 5 formed on the second main surface of the reflectivemask 200 and is mounted on a mask stage.

The light of the EUV light source is applied to the reflective mask 200through the illumination optical system at an angle tilted by 6 to 8degrees with respect to a vertical plane of the reflective mask 200.Reflected light from the reflective mask 200 with respect to thisincident light (exposure light) is reflected (regularly reflected) in adirection opposite to an incident direction and at the same angle as anincident angle, guided to a reflective projection system usually havinga reduction ratio of 1/4, and exposed on a resist on a wafer (thesemiconductor substrate) mounted on a wafer stage. During this time, atleast a place through which EUV light passes is evacuated. In addition,when exposure is performed, mainstream exposure is scan exposure inwhich the mask stage and the wafer stage are synchronously scanned at aspeed corresponding to the reduction ratio of the reduction projectionoptical system, and exposure is performed through a slit. After theexposure on the resist, this resist film subjected to the exposure isdeveloped, whereby a resist pattern can be formed on the semiconductorsubstrate. In the present embodiment, the mask having the highlyaccurate phase shift pattern that is a thin film and has a smallshadowing effect and small sidewall roughness is used. Therefore, theresist pattern formed on the semiconductor substrate is desired one withhigh dimensional accuracy. Etching or the like is performed using thisresist pattern as a mask, whereby a predetermined wiring pattern can beformed, for example, on the semiconductor substrate. The semiconductordevice is manufactured through such an exposure step, a step ofprocessing a film to be processed, a step of forming an insulating filmand a conductive film, a dopant introduction step, an annealing step,and other necessary steps.

According to the method of manufacturing a semiconductor device of thepresent embodiment, the reflective mask 200 capable of reducing the filmthickness of the phase shift film 4, reducing the shadowing effect, andforming the fine and highly accurate phase shift pattern 4 a in a stablecross-sectional shape with small sidewall roughness can be used formanufacturing a semiconductor device. Thus, a semiconductor devicehaving a fine and highly accurate transfer pattern can be manufactured.

EXAMPLES

Hereinafter, Examples will be described with reference to the drawings.The present disclosure is not limited to these Examples. Note that inExamples, the same reference signs will be used for similar constituentelements, and the description thereof will be simplified or omitted.

Example 1

FIGS. 2A-2E are schematic cross-sectional diagrams of a main partshowing a step of manufacturing a reflective mask 200 from a reflectivemask blank 100.

The reflective mask blank 100 has a back side conductive film 5, asubstrate 1, a multilayer reflective film 2, a protective film 3, and aphase shift film 4. The phase shift film 4 of Example 1 has a lowerlayer 41 (a first layer) that is a TaN film and an upper layer 42 thatis a RuCr film (a second layer). Then, as shown in FIG. 2A, a resistfilm 11 is formed on the phase shift film 4.

First, the reflective mask blank 100 of Example 1 will be described.

A SiO₂—TiO₂-based glass substrate that is a low thermal expansion glasssubstrate having 6025 size (approximately 152 mm×152 mm×6.35 mm) andhaving polished both main surfaces that are a first main surface and asecond main surface was prepared as the substrate 1. The main surfaceswas subjected to polishing including a rough polishing step, a precisionpolishing step, a local processing step, and a touch polishing step sothat the main surfaces were flat and smooth.

Next, the back side conductive film 5 including a CrN film was formed onthe second main surface (a back surface) of the SiO₂—TiO₂-based glasssubstrate (the substrate 1) by a magnetron sputtering (a reactivesputtering) method under the following conditions.

Conditions for forming the back side conductive film 5: a Cr target, amixed gas atmosphere of Ar and N₂ (Ar: 90%, N: 10%), and a filmthickness of 20 nm.

Next, the multilayer reflective film 2 was formed on the main surface(the first main surface) of the substrate 1 on a side opposite to a sideon which the back side conductive film 5 is formed. The multilayerreflective film 2 formed on the substrate 1 was a periodic multilayerreflective film including Mo and Si in order to be the multilayerreflective film 2 suitable for EUV light having a wavelength of 13.5 nm.The multilayer reflective film 2 was formed by using a Mo target and aSi target and alternately building up a Mo layer and a Si layer on thesubstrate 1 in an Ar gas atmosphere by an ion beam sputtering method.First, a Si film was formed to have a film thickness of 4.2 nm, and thena Mo film was formed to have a film thickness of 2.8 nm. This stack iscounted as one period, the stack of a Si film and a Mo film was built upfor 40 periods in a similar manner, and finally, a Si film was formed tohave a film thickness of 4.0 nm to form the multilayer reflective film2. The number of periods was 40 periods here, but the number of periodsis not limited to this number and may be, for example, 60 periods. Inthe case of 60 periods, the number of steps is larger than the number ofsteps in the case of 40 periods, but reflectance for EUV light can beincreased.

Subsequently, the protective film 3 including a Ru film was formed tohave a film thickness of 2.5 nm using a Ru target in an Ar gasatmosphere by an ion beam sputtering method.

Next, the first layer including the TaN film was formed as the lowerlayer 41 of the phase shift film 4 by the DC magnetron sputteringmethod. The TaN film was formed so as to have a film thickness of 15.5nm using a Ta target in a N₂ gas atmosphere by the reactive sputtering.The content ratio (the atomic ratio) of the TaN film was Ta:N=88:12.When the crystal structure of the TaN film was measured by an X-raydiffractometer (XRD), the TaN film had an amorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the TaN film of Example 1 formed as describedabove at a wavelength of 13.5 nm were as follows, respectively.

The TaN film: n=0.949 and k=0.032

Next, the second layer including the RuCr film was formed as the upperlayer 42 of the phase shift film 4 by the DC magnetron sputteringmethod. The RuCr film was formed so as to have a film thickness of 22.8nm using a RuCr target in an Ar gas atmosphere. The content ratio (theatomic ratio) of the RuCr film was Ru:Cr=90:10. When the crystalstructure of the RuCr film was measured by the X-ray diffractometer(XRD), the RuCr film had an amorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the RuCr film of Example 1 formed asdescribed above at a wavelength of 13.5 nm of were as follows,respectively.

The RuCr film: n=0.890 and k=0.019

The relative reflectance of the phase shift film 4 including the TaNfilm and the RuCr film described above at a wavelength of 13.5 nm was20.1%. In addition, the total film thickness of the phase shift film 4is 38.3 nm. At this film thickness, a phase difference when the phaseshift film 4 was patterned corresponds to 180 degrees. The filmthickness was reduced by approximately 41% from 65 nm that is the filmthickness of a phase shift film 4 that is a TaN film in ComparativeExample 1 to be described later.

Next, the reflective mask 200 was manufactured using the reflective maskblank 100 described above.

The resist film 11 was formed with a thickness of 100 nm (FIG. 2A) onthe phase shift film 4 of the reflective mask blank 100. Then, a desiredpattern was drawn (exposed) on this resist film 11 and further developedand rinsed, whereby a predetermined resist pattern 11 a was formed (FIG.2B).

Next, using the resist pattern 11 a as a mask, the RuCr film (the upperlayer 42) was subjected to dry etching using a mixed gas of a Cl₂ gasand an O₂ gas (gas flow rate ratio Cl₂:O₂=4:1). As a result, an upperlayer pattern 42 a was formed (FIG. 2C).

Next, using the resist pattern 11 a and the upper layer pattern 42 a asa mask, the TaN film (the lower layer 41) was subjected to dry etchingusing a halogen-based gas. As a result, the lower layer pattern 41 a wasformed (FIG. 2D). Specifically, an oxide film that is a surface layer ofthe TaN film was subjected to dry etching using a CF₄ gas, and then theTaN film was subjected to dry etching using a Cl₂ gas.

Thereafter, the resist pattern 11 a was removed by ashing, a resiststripping solution, or the like. Finally, wet cleaning was performedwith deionized water (DIW) to manufacture the reflective mask 200 ofExample 2 (FIG. 2E). Note that a mask defect inspection is performed, ifnecessary after the wet cleaning, and a mask defect can be correctedappropriately.

In the reflective mask 200 of Example 1, since the phase shift film 4 isthe TaN film and the RuCr film, workability in dry etching using apredetermined etching gas is good, and a phase shift pattern 4 a wasformed highly accurately. In addition, the total film thickness of thephase shift pattern 4 a is 38.3 nm, and was made thinner than that of anabsorber film formed of a conventional Ta-based material, and theshadowing effect was reduced as compared with Comparative Example 1.

In addition, since in the reflective mask 200 created in Example 1, thesidewall roughness of the phase shift pattern 4 a is small and thecross-sectional shape thereof is stable, the reflective mask 200 hadhigh transfer accuracy with little variations in line edge roughness(LER) and in-plane dimensions of a transferred and formed resistpattern. In addition, as described above, since the relative reflectanceof a phase shift surface (a reflectance with respect to the reflectanceof a surface of the multilayer reflective film 2 with the protectivefilm 3) is 20.1%, a sufficient phase shift effect was obtained, and EUVexposure with a high exposure margin and a high focus margin wasperformed.

The reflective mask 200 manufactured in Example 1 was set in an EUVexposure scanner, and EUV exposure was performed on a wafer on which afilm to be processed and a resist film were formed on a semiconductorsubstrate. Then, this resist film subjected to the exposure wasdeveloped, whereby a resist pattern was formed on the semiconductorsubstrate on which the film to be processed was formed. In addition,this resist pattern was transferred on the film to be processed byetching, and a semiconductor device having desired characteristics wasmanufactured by being subjected to various steps such as formation of aninsulating film and a conductive film, introduction of a dopant, andannealing,

Example 2

Example 2 is an example in a case where a lower layer 41 that is a CrOCfilm (a first layer) and an upper layer 42 that is a RuNi film (a secondlayer) were used as a phase shift film 4 and film thickness was adjustedso that a phase difference of 180 degrees was obtained. Example 2 is thesame as Example 1 except for the above.

That is, in Example 2, as in Example 1, a back side conductive film 5including a CrN film was formed on a second main surface (a backsurface) of a SiO₂—TiO₂ glass substrate 1, a multilayer reflective film2 was formed on a main surface (a first main surface) of the substrate 1on an opposite side, and a protective film 3 including a Ru film wasformed on a surface of a multilayer reflective film 2.

Next, the first layer including the CrOC film was formed as the lowerlayer 41 of the phase shift film 4 by a DC magnetron sputtering method.The CrOC film was formed so as to have a film thickness of 13.8 nm usinga Cr target by reactive sputtering using a mixed gas of an Ar gas, a CO₂gas, and a He gas. The content ratio (the atomic ratio) of the CrOC filmwas Cr:O:C=70:15:15. When the crystal structure of the CrOC film wasmeasured by an X-ray diffractometer (XRD), the CrOC film had anamorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the CrOC film of Example 2 formed asdescribed above at a wavelength of 13.5 nm were as follows,respectively.

The CrOC film: n=0.941 and k=0.031

Next, the second layer including the RuNi film was formed as the upperlayer 42 of the phase shift film 4 by the DC magnetron sputteringmethod. The RuNi film was formed so as to have a film thickness of 23.5nm using a RuNi target in an Ar gas atmosphere. The content ratio (theatomic ratio) of the RuNi film was Ru:Ni=90:10. When the crystalstructure of the RuNi film was measured by the X-ray diffractometer(XRD), the RuNi film had an amorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the RuNi film of Example 2 formed asdescribed above at a wavelength of 13.5 nm were as follows,respectively.

The RuNi film: n=0.891 and k=0.022

The relative reflectance of the phase shift film 4 including the CrOCfilm and the RuNi film at a wavelength of 13.5 nm was 20.2%. Inaddition, the total film thickness of the phase shift film 4 is 37.3 nm.At this film thickness, a phase difference when the phase shift film 4was patterned corresponds to 180 degrees. The film thickness was reducedby approximately 43% from 65 nm that is the thickness of the phase shiftfilm 4 that is a TaN film in Comparative Example 1 to be describedlater.

Next, as in Example 1, a reflective mask 200 of Example 2 wasmanufactured using the reflective mask blank 100 described above.

As in Example 1, a resist film 11 was formed with a thickness of 100 nmon the phase shift film 4 of the reflective mask blank 100 (FIG. 2A).Then, a desired pattern was drawn (exposed) on this resist film 11 andfurther developed and rinsed, whereby a predetermined resist pattern 11a was formed (FIG. 2B).

Next, using the resist pattern 11 a as a mask, the RuNi film (the upperlayer 42) was subjected to dry etching using an O₂ gas. As a result, anupper layer pattern 42 a was formed (FIG. 2C).

Next, using the resist pattern 11 a and the upper layer pattern 42 a asa mask, the CrOC film (the lower layer 41) was subjected to dry etchingusing a Cl₂ gas. As a result, a lower layer pattern 41 a was formed(FIG. 2D).

Thereafter, as in Example 1, the resist pattern 11 a was removed andcleaned to manufacture the reflective mask 200 of Example 2 (FIG. 2E).

In the reflective mask 200 of Example 2, since the phase shift film 4 isthe CrOC film and the RuNi film, workability in dry etching using apredetermined etching gas is good, and a phase shift pattern 4 a wasformed highly accurately. In addition, the total film thickness of thephase shift pattern 4 a is 37.3 nm and was made thinner than that of theabsorber film formed of the conventional Ta-based material, and theshadowing effect was reduced as compared with Comparative Example 1.

In addition, since in the reflective mask 200 created in Example 2, thesidewall roughness of the phase shift pattern 4 a is small and thecross-sectional shape thereof is stable, the reflective mask 200 hadhigh transfer accuracy with little variations in LER and in-planedimensions of a transferred and formed resist pattern. In addition, asdescribed above, since the relative reflectance of the phase shiftsurface is 20.2%, a sufficient phase shift effect was obtained, and EUVexposure with a high exposure margin and a high focus margin wasperformed.

As in the case of Example 1, using the reflective mask 200 manufacturedin Example 2, a semiconductor device having desired characteristics wasmanufactured.

Example 3

Example 3 is an example in a case where a SiO₂ film was used as aprotective film 3, a lower layer 41 that is a RuCo film (a second layer)and an upper layer 42 that is a TaN film (a first layer) were used as aphase shift film 4, and film thickness was adjusted so that a phasedifference of 180 degrees was obtained. Example 3 is the same as Example1 except for the above.

That is, in Example 3, as in Example 1, a back side conductive film 5including a CrN film was formed on a second main surface (a backsurface) of a SiO₂—TiO₂ glass substrate 1, a multilayer reflective film2 was formed on a main surface (a first main surface) of the substrate 1on an opposite side.

Subsequently, the protective film 3 including the SiO₂ film was formedto have a film thickness of 2.5 nm on a surface of the multilayerreflective film 2 in an Ar gas atmosphere by an RF sputtering methodusing a SiO₂ target.

Next, the second layer including the RuCo film was formed as the lowerlayer 41 of the phase shift film 4 by a DC magnetron sputtering method.The RuCo film was formed so as to have a film thickness of 23.2 nm usinga RuCo target in an Ar gas atmosphere. The content ratio (the atomicratio) of the RuCo film was Ru:Co=90:10. When the crystal structure ofthe RuCo film was measured by an X-ray diffractometer (XRD), the RuCofilm had an amorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the RuCo film of Example 3 formed asdescribed above at a wavelength of 13.5 nm were as follows,respectively.

The RuCo film: n=0.890 and k=0.021

Next, the first layer including the TaN film was formed as the upperlayer 42 of the phase shift film 4 by the DC magnetron sputteringmethod. The TaN film was formed so as to have a film thickness of 13.9nm using a Ta target in a N₂ gas atmosphere by reactive sputtering. Thecontent ratio (the atomic ratio) of the TaN film was Ta:N=88:12. Whenthe crystal structure of the TaN film was measured by an X-raydiffractometer (XRD), the TaN film had an amorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the TaN film of Example 3 formed as describedabove at a wavelength of 13.5 nm were as follows, respectively.

The TaN film: n=0.949 and k=0.032

The relative reflectance of the phase shift film 4 including the RuCofilm and the TaN film described above at a wavelength of 13.5 nm was19.9%. In addition, the total film thickness of the phase shift film 4is 37.1 nm. At this film thickness, a phase difference when the phaseshift film 4 was patterned corresponds to 180 degrees. The filmthickness was reduced by approximately 43% from 65 nm that is thethickness of the phase shift film 4 that is a TaN film in ComparativeExample 1 to be described later.

Next, as in Example 1, a reflective mask 200 of Example 3 wasmanufactured using the reflective mask blank 100 described above.

As in Example 1, a resist film 11 was formed with a thickness of 100 nmon the phase shift film 4 of the reflective mask blank 100 (FIG. 2A).Then, a desired pattern was drawn (exposed) on this resist film 11 andfurther developed and rinsed, whereby a predetermined resist pattern 11a was formed (FIG. 2B).

Next, the resist pattern 11 a was used as a mask and the TaN film (theupper layer 42) was subjected to dry etching using etching by ahalogen-based gas. As a result, an upper layer pattern 42 a was formed(FIG. 2C). Specifically, an oxide film that is a surface layer of theTaN film was subjected to dry etching using a CF₄ gas, and then the TaNfilm was subjected to dry etching using a Cl₂ gas.

Next, using the resist pattern 11 a and the upper layer pattern 42 a asa mask, the RuCo film (the lower layer 41) was subjected to dry etchingusing a mixed gas of a Cl₂ gas and an O₂ gas (gas flow rate ratioCl₂:O₂=4:1). As a result, a lower layer pattern 41 a was formed (FIG.2D).

Thereafter, as in Example 1, the resist pattern 11 a was removed andcleaned to manufacture the reflective mask 200 of Example 3 (FIG. 2E).

In the reflective mask 200 of Example 3, since the phase shift film 4 isthe TaN film and the RuCo film, workability in dry etching using apredetermined etching gas is good, and a phase shift pattern 4 a wasformed highly accurately. In addition, the total film thickness of thephase shift pattern 4 a is 37.1 nm and was made thinner than that of theabsorber film formed of the conventional Ta-based material, and theshadowing effect was reduced as compared with Comparative Example 1.

In addition, since in the reflective mask 200 created in Example 3, thesidewall roughness of the phase shift pattern 4 a is small and thecross-sectional shape thereof is stable, the reflective mask 200 hadhigh transfer accuracy with little variations in LER and in-planedimensions of a transferred and formed resist pattern. In addition, asdescribed above, since the relative reflectance of the phase shiftsurface is 19.9%, a sufficient phase shift effect was obtained, and EUVexposure with a high exposure margin and a high focus margin wasperformed.

As in the case of Example 1, using the reflective mask 200 manufacturedin Example 3, a semiconductor device having desired characteristics wasmanufactured.

Example 4

Example 4 is an example in a case where a lower layer 41 that is a RuCrfilm (a second layer) and an upper layer 42 that is a CrOC film (a firstlayer) as a phase shift film 4, and film thickness was adjusted so thata phase difference of 180 degrees was obtained. Example 4 is the same asExample 3 except for the above.

That is, in Example 4, as in Example 3, a back side conductive film 5including a CrN film was formed on a second main surface (a backsurface) of a SiO₂—TiO₂ glass substrate 1, and a multilayer reflectivefilm 2 and a protective film 3 of a SiO₂ film were formed on a mainsurface (a first main surface) of the substrate 1 on an opposite side.

Next, the second layer including the RuCr film was formed as the lowerlayer 41 of the phase shift film 4 by a DC magnetron sputtering method.The RuCr film was formed so as to have a film thickness of 22.2 nm usinga RuCr target in an Ar gas atmosphere. The content ratio (the atomicratio) of the RuCr film was Ru:Cr=90:10. When the crystal structure ofthe RuCr film was measured by the X-ray diffractometer (XRD), the RuCrfilm had an amorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the RuCr film of Example 4 formed asdescribed above at a wavelength of 13.5 nm were as follows,respectively.

The RuCr film: n=0.890 and k=0.019

Next, the first layer including the CrOC film was formed as the upperlayer 42 of the phase shift film 4 by the DC magnetron sputteringmethod. The CrOC film was formed so as to have a film thickness of 15.4nm using a Cr target by reactive sputtering using a mixed gas of an Argas, a CO₂ gas, and a He gas. The content ratio (the atomic ratio) ofthe CrOC film was Cr:O:C=70:15:15. When the crystal structure of theCrOC film was measured by an X-ray diffractometer (XRD), the CrOC filmhad an amorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the CrOC film of Example 4 formed asdescribed above at a wavelength of 13.5 nm were as follows,respectively.

The CrOC film: n=0.941 and k=0.031

The relative reflectance of the phase shift film 4 including the aboveRuCr film and CrOC film described above at a wavelength of 13.5 nm was20.2%. In addition, the total film thickness of the phase shift film 4is 37.6 nm. At this film thickness, a phase difference when the phaseshift film 4 was patterned corresponds to 180 degrees. The filmthickness was reduced by approximately 42% from 65 nm that is thethickness of a phase shift film 4 that is a TaN film in ComparativeExample 1 to be described later.

Next, as in Example 1, a reflective mask 200 of Example 4 wasmanufactured using the reflective mask blank 100 described above.

As in Example 1, a resist film 11 was formed with a thickness of 100 nmon the phase shift film 4 of the reflective mask blank 100 (FIG. 2A).Then, a desired pattern was drawn (exposed) on this resist film 11 andfurther developed and rinsed, whereby a predetermined resist pattern 11a was formed (FIG. 2B).

Next, using the resist pattern 11 a as a mask, the CrOC film (the upperlayer 42) was subjected to dry etching using a mixed gas of a Cl₂ gasand an O₂ gas (gas flow rate ratio Cl₂:O₂=4:1). As a result, an upperlayer pattern 42 a was formed (FIG. 2C).

Subsequently, the RuCr film (the lower layer 41) was subjected to dryetching using the same mixed gas as that for the CrOC film (the upperlayer 42) (a mixed gas of a Cl₂ gas and an O₂ gas (gas flow rate ratioCl₂:O₂=4:1)). As a result, a lower layer pattern 41 a was formed (FIG.2D). The upper layer 42 and the lower layer 41 were consecutivelysubjected to dry etching.

Thereafter, as in Example 1, the resist pattern 11 a was removed andcleaned to manufacture the reflective mask 200 of Example 4 (FIG. 2E).

In the reflective mask 200 of Example 4, since the phase shift film 4 isthe CrOC film and the RuCr film, workability in dry etching using apredetermined etching gas is good, and a phase shift pattern 4 a wasformed highly accurately. In addition, since both the CrOC film and theRuCr film were consecutively etched using the same etching gas,productivity is high. In addition, the total film thickness of the phaseshift pattern 4 a is 37.6 nm and was made thinner than that of theabsorber film formed of the conventional Ta-based material, and theshadowing effect was reduced as compared with Comparative Example 1.

In addition, since in the reflective mask 200 created in Example 4, thesidewall roughness of the phase shift pattern 4 a is small and thecross-sectional shape thereof is stable, the reflective mask 200 hadhigh transfer accuracy with little variations in LER and in-planedimensions of a transferred and formed resist pattern. In addition, asdescribed above, since the relative reflectance of the phase shiftsurface is 20.2%, a sufficient phase shift effect was obtained, and EUVexposure with a high exposure margin and a high focus margin wasperformed.

As in the case of Example 1, using the reflective mask 200 manufacturedin Example 4, a semiconductor device having desired characteristics wasmanufactured.

Example 5

Example 5 is an example in a case where a RuNb film was used as aprotective film 3, a lower layer 41 that is a TaN film (a first layer)and an upper layer 42 that is a RuNb film (a second layer) were used asa phase shift film 4, and film thickness was adjusted so that a phasedifference of 180 degrees was obtained. Example 5 is the same as Example1 except for the above.

That is, in Example 5, the protective film 3 including the RuNb film wasformed on a surface of a multilayer reflective film 2 similar to that inExample 1. The RuNb film was formed so as to have a film thickness of2.5 nm using a RuNb target in an Ar gas atmosphere. The content ratio(the atomic ratio) of the RuNb film was Ru:Nb=80:20.

Next, the first layer including the TaN film was formed on the RuNbfilm, as the lower layer 41 of the phase shift film 4. The TaN film wasformed to have a film thickness of 16.5 nm by a film forming methodsimilar to that in Example 1. The refractive index n and the extinctioncoefficient k at a wavelength of 13.5 nm of the TaN film were the sameas those in Example 1.

Thereafter, the second layer including the RuNb film was formed as theupper layer 42 of the phase shift film 4 by a DC magnetron sputteringmethod. The RuNb film was formed so as to have a film thickness of 22.9nm using a RuNb target in an Ar gas atmosphere. The content ratio (theatomic ratio) of the RuNb film was Ru:Nb=80:20. When the crystalstructure of the RuNb film was measured by an X-ray diffractometer(XRD), the RuNb film had an amorphous structure.

The refractive index n and the extinction coefficient k of the RuNb filmof Example 5 formed as described above at a wavelength of 13.5 nm wereas follows, respectively.

The RuNb film: n=0.897 and k=0.014

The relative reflectance of the phase shift film 4 described above at awavelength of 13.5 nm was 19.6% (the absolute reflectance was 13.1%). Inaddition, the total film thickness of the phase shift film 4 is 39.4 nm.At this film thickness, a phase difference when the phase shift film 4was patterned corresponds to 180 degrees. The film thickness was reducedby approximately 39% from 65 nm that is the thickness of the phase shiftfilm 4 that is a TaN film in Comparative Example 1 to be describedlater.

Next, as in Example 1, a reflective mask 200 of Example 5 wasmanufactured using the reflective mask blank 100 described above. TheRuNb film was subjected to dry etching using a mixed gas of a Cl₂ gasand an O₂ gas (gas flow rate ratio Cl₂:O₂=4:1). An oxide film that is asurface layer of the TaN film was subjected to dry etching using a CF₄gas, and then the TaN film was subjected to dry etching using a Cl₂ gas.

In the reflective mask 200 of Example 5, since the phase shift film 4 isthe TaN film and the RuNb film, workability in dry etching using apredetermined etching gas is good, and a phase shift pattern 4 a wasformed highly accurately. In addition, the total film thickness of thephase shift pattern 4 a is 39.4 nm, and was made thinner than that ofthe absorber film formed of the conventional Ta-based material, and theshadowing effect was reduced as compared with Comparative Example 1.

In addition, since in the reflective mask 200 created in Example 5, thesidewall roughness of the phase shift pattern 4 a is small and thecross-sectional shape thereof is stable, the reflective mask 200 hadhigh transfer accuracy with little variations in LER and in-planedimensions of a transferred and formed resist pattern. In addition, asdescribed above, since the relative reflectance of the phase shiftsurface is 19.6% (the absolute reflectance was 13.1%), a sufficientphase shift effect was obtained, and EUV exposure with a high exposuremargin and a high focus margin was performed.

As in the case of Example 1, using the reflective mask 200 manufacturedin Example 5, a semiconductor device having desired characteristics wasmanufactured.

Example 6

Example 6 is an example in a case where a RuNb film was used as aprotective film 3, a lower layer 41 that is a CrOC film (a first layer)and an upper layer 42 that is a RuV film (a second layer) were used as aphase shift film 4, and film thickness was adjusted so that a phasedifference of 180 degrees was obtained. Example 6 is the same as Example1 except for the above.

That is, in Example 6, the protective film 3 including a RuNb filmsimilar to that in Example 5 was formed on the surface of a multilayerreflective film 2 similar to that in Example 1.

Next, a first layer including the CrOC film was formed on the RuNb film,as the lower layer 41 of the phase shift film 4. The CrOC film wasformed so as to have a film thickness of 14.7 nm by a film formingmethod similar to that in Example 2. The refractive index n and theextinction coefficient k at a wavelength of 13.5 nm of the CrOC filmwere the same as those in Example 2.

Thereafter, the second layer including the RuV film was formed as theupper layer 42 of the phase shift film 4 by a DC magnetron sputteringmethod. The RuV film was formed so as to have a film thickness of 24 nmusing a RuV target in an Ar gas atmosphere. The content ratio (theatomic ratio) of the RuV film was Ru:V=70:30. When the crystal structureof the RuV film was measured by the X-ray diffractometer (XRD), the RuVfilm had an amorphous structure.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the RuV film of Example 6 formed as describedabove at a wavelength of 13.5 nm were as follows, respectively.

The RuV film: n=0.903 and k=0.020

The relative reflectance of the phase shift film 4 described above at awavelength of 13.5 nm was 20.1% (the absolute reflectance was 13.4%). Inaddition, the total film thickness of the phase shift film 4 is 38.7 nm.At this film thickness, a phase difference when the phase shift film 4was patterned corresponds to 180 degrees. The film thickness was reducedby approximately 40% from 65 nm that is the thickness of the phase shiftfilm 4 that is a TaN film in Comparative Example 1 to be describedlater.

Next, as in Example 1, a reflective mask 200 of Example 6 wasmanufactured using the reflective mask blank 100 described above. TheRuV film was subjected to dry etching using a mixed gas of a Cl₂ gas andan O₂ gas (gas flow rate ratio Cl₂:O₂=4:1). The CrOC film was subjectedto dry etching using a Cl₂ gas.

In the reflective mask 200 of Example 6, since the phase shift film 4 isthe CrOC film and the RuV film, workability in dry etching using apredetermined etching gas is good, and a phase shift pattern 4 a wasformed highly accurately. In addition, the total film thickness of thephase shift pattern 4 a is 38.7 nm and was made thinner than that of theabsorber film formed of the conventional Ta-based material, and theshadowing effect was reduced as compared with Comparative Example 1.

In addition, since in the reflective mask 200 created in Example 6, thesidewall roughness of the phase shift pattern 4 a is small and thecross-sectional shape thereof is stable, the reflective mask 200 hadhigh transfer accuracy with little variations in LER and in-planedimensions of a transferred and formed resist pattern. In addition, asdescribed above, since the relative reflectance of the phase shiftsurface is 20.1% (the absolute reflectance was 13.4%), a sufficientphase shift effect was obtained, and EUV exposure with a high exposuremargin and a high focus margin was performed.

As in the case of Example 1, using the reflective mask 200 manufacturedin Example 6, a semiconductor device having desired characteristics wasmanufactured.

Example 7

Example 7 is an example in a case where an SiO₂ film was used as aprotective film 3, a lower layer 41 that is a RuV film (a second layer)and an upper layer 42 that is a TaN film (a first layer) were used as aphase shift film 4, and film thickness was adjusted so that a phasedifference of 180 degrees was obtained. Example 7 is the same as Example1 except for the above.

That is, in Example 7, the protective film 3 including the SiO₂ filmsimilar to that in Example 3 was formed on a surface of a multilayerreflective film 2 similar to that in Example 1.

Next, the second layer including the RuV film was formed on the SiO₂film, as the lower layer 41 of the phase shift film 4. The RuV film wasformed so as to have a film thickness of 29 nm by a film forming methodsimilar to that in Example 6. The refractive index n and the extinctioncoefficient k at a wavelength of 13.5 nm of the RuV film were the sameas those in Example 6.

Thereafter, the second layer including the TaN film was formed as theupper layer 42 of the phase shift film 4. The TaN film was formed so asto have a film thickness of 9.2 nm by a film forming method similar tothat in Example 1. The refractive index n and the extinction coefficientk at a wavelength of 13.5 nm of the TaN film were the same as those inExample 1.

The relative reflectance of the phase shift film 4 described above at awavelength of 13.5 nm was 19.9% (the absolute reflectance was 13.3%). Inaddition, the total film thickness of the phase shift film 4 is 33.2 nm.At this film thickness, a phase difference when the phase shift film 4was patterned corresponds to 180 degrees. The film thickness was reducedby approximately 49% from 65 nm that is the thickness of the phase shiftfilm 4 that is a TaN film in Comparative Example 1 to be describedlater.

Next, as in Example 1, a reflective mask 200 of Example 7 wasmanufactured using the reflective mask blank 100 described above. Anoxide film that is a surface layer of the TaN film was subjected to dryetching using a CF₄ gas, and then the TaN film was subjected to dryetching using a Cl₂ gas. The RuV film was subjected to dry etching usinga mixed gas of a Cl₂ gas and an O₂ gas (gas flow rate ratio Cl₂:O₂=4:1).

In the reflective mask 200 of Example 7, since the phase shift film 4 isthe RuV film and the TaN film, workability in dry etching using apredetermined etching gas is good, and a phase shift pattern 4 a wasformed highly accurately. In addition, the total film thickness of thephase shift pattern 4 a is 39.4 nm, and was made thinner than that ofthe absorber film formed of the conventional Ta-based material, and theshadowing effect was reduced as compared with Comparative Example 1.

In addition, since in the reflective mask 200 created in Example 7, thesidewall roughness of the phase shift pattern 4 a is small and thecross-sectional shape thereof is stable, the reflective mask 200 hadhigh transfer accuracy with little variations in LER and in-planedimensions of a transferred and formed resist pattern. In addition, asdescribed above, since the relative reflectance of the phase shiftsurface is 19.9% (the absolute reflectance was 13.3%), a sufficientphase shift effect was obtained, and EUV exposure with a high exposuremargin and a high focus margin was performed.

As in the case of Example 1, using the reflective mask 200 manufacturedin Example 7, a semiconductor device having desired characteristics wasmanufactured.

Example 8

Example 8 is an example in a case where an SiO₂ film was used as aprotective film 3, a lower layer 41 that is a RuNb film (a second layer)and an upper layer 42 that is a CrOC film (a first layer) were used as aphase shift film 4, and film thickness was adjusted so that a phasedifference of 180 degrees was obtained. Example 8 is the same as Example1 except for the above.

That is, in Example 8, the protective film 3 including the SiO₂ filmsimilar to that in Example 3 was formed on a surface of a multilayerreflective film 2 similar to that in Example 1.

Next, the second layer including the RuNb film was formed on the SiO₂film, as the lower layer 41 of the phase shift film 4. The RuNb film wasformed so as to have a film thickness of 18.3 nm by a film formingmethod similar to that in Example 5. The refractive index n and theextinction coefficient k at a wavelength of 13.5 nm of the RuNb filmwere the same as those in Example 5.

Thereafter, the second layer including the CrOC film was formed as theupper layer 42 of the phase shift film 4. The CrOC film was formed so asto have a film thickness of 20.7 nm by a film forming method similar tothat in Example 1. The refractive index n and the extinction coefficientk at a wavelength of 13.5 nm of the CrOC film were the same as those inExample 2.

The relative reflectance of the phase shift film 4 described above at awavelength of 13.5 nm was 19.7% (the absolute reflectance was 13.1%). Inaddition, the total film thickness of the phase shift film 4 is 39 nm.At this film thickness, a phase difference when the phase shift film 4was patterned corresponds to 180 degrees. The film thickness was reducedby about 40% from 65 nm that is the thickness of the phase shift film 4that is a TaN film in Comparative Example 1 to be described later.

Next, as in Example 1, a reflective mask 200 of Example 8 wasmanufactured using the reflective mask blank 100 described above. TheCrOC film and the RuNb film were subjected to dry etching using a mixedgas of a Cl₂ gas and an O₂ gas (gas flow rate ratio Cl₂:O₂=4:1).

In the reflective mask 200 of Example 8, since the phase shift film 4 isthe RuNb film and a CrOC film, workability in dry etching using apredetermined etching gas is good, and a phase shift pattern 4 a wasformed highly accurately. In addition, the total film thickness of thephase shift pattern 4 a is 39 nm and was made thinner than that of theabsorber film formed of the conventional Ta-based material, and theshadowing effect was reduced as compared with Comparative Example 1.

In addition, since in the reflective mask 200 created in Example 8, thesidewall roughness of the phase shift pattern 4 a is small and thecross-sectional shape thereof is stable, the reflective mask 200 hadhigh transfer accuracy with little variations in LER and in-planedimensions of a transferred and formed resist pattern. In addition, asdescribed above, since the relative reflectance of the phase shiftsurface is 19.7% (the absolute reflectance was 13.1%), a sufficientphase shift effect was obtained, and EUV exposure with a high exposuremargin and a high focus margin was performed.

As in the case of Example 1, using the reflective mask 200 manufacturedin Example 8, a semiconductor device having desired characteristics wasmanufactured.

Comparative Example 1

In Comparative Example 1, a reflective mask blank 100 and a reflectivemask 200 were each manufactured to have a structure similar to that inExample 1 by a method similar to that in Example 1, and a semiconductordevice was manufactured by a method similar to that in Example 1, exceptthat in Comparative Example 1, a single-layer TaN film was used as aphase shift film 4.

The single-layer TaN film (the phase shift film 4) was formed on aprotective film 3 having a mask blank structure of Example 1. By amethod of forming this TaN film, a TaN film was formed using Ta as atarget by reactive sputtering in a mixed gas atmosphere of a Xe gas anda N₂ gas. The film thickness of the TaN film is 65 nm, and the elementratio of this film is 88 atomic % for Ta and 12 atomic % for N.

The refractive index n and the extinction coefficient (the refractiveindex imaginary part) k of the TaN film formed as described above at awavelength of 13.5 nm were as follows, respectively.

The TaN film: n=0.949 and k=0.032

The phase difference of the phase shift film 4 including thesingle-layer TaN film described above at a wavelength of 13.5 nm is 180degrees. The reflectance was 1.7% with respect to the multilayerreflective film 2 surface.

Thereafter, a resist film 11 was formed on the phase shift film 4including the single-layer TaN film by a method similar to that inExample 1, and a desired pattern was drawn (exposed) and developed andrinsed, whereby a resist pattern 11 a was formed. Then, using the resistpattern 11 a as a mask, the phase shift film 4 including thesingle-layer TaN film was subjected to dry etching using a chlorine gasto form a phase shift pattern 4 a. Removal of the resist pattern 11 a,cleaning of the mask, and the like were performed in the same manner asthat in Example 1 to manufacture the reflective mask 200.

The film thickness of the phase shift pattern 4 a was 65 nm, and theshadowing effect could not be reduced. In addition, as described above,since the relative reflectance of the phase shift surface (reflectancewith respect to the reflectance of the multilayer reflective filmsurface with a protective film) was 1.7%, a sufficient phase shifteffect could not be obtained, and EUV exposure with a high exposuremargin and a high focus margin could not be performed.

As described above, the total film thickness of the phase shift film 4of each of Examples 1 to 8 was reduced by approximately 40% or more from65 nm that is the film thickness of the phase shift film 4 ofComparative Example 1. Thus, it was revealed that the shadowing effectcan be reduced with the reflective masks 200 of Examples 1 to 8.

REFERENCE SIGNS LIST

-   1 Substrate-   2 Multilayer reflective film-   3 Protective film-   4 Phase shift film-   4 a Phase shift pattern-   41 Lower layer-   41 a Lower layer pattern-   42 Upper layer-   42 a Upper layer pattern-   5 Back side conductive film-   11 Resist film-   11 a Resist pattern-   100 Reflective mask blank-   200 Reflective mask

1. A reflective mask blank comprising: a substrate; a multilayerreflective film on the substrate; and on the multilayer reflective film,a phase shift film for shifting a phase of EUV light, wherein the phaseshift film comprises a first layer and a second layer, the first layercomprises at least one selected from of tantalum (Ta) and chromium (Cr),and the second layer comprises ruthenium (Ru) and at least one selectedfrom chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V), niobium(Nb), molybdenum (Mo), tungsten (W), and rhenium (Re).
 2. The reflectivemask blank according to claim 1, wherein the second layer comprisesruthenium (Ru) and at least one selected from chromium (Cr), nickel(Ni), and cobalt (Co).
 3. The reflective mask blank according to claim1, further comprising a protective film between the multilayerreflective film and the phase shift film, wherein the protective film ismade of a material containing ruthenium (Ru), and the first layer andthe second layer are layered in this order on the protective film. 4.The reflective mask blank according to claim 1, further comprising aprotective film between the multilayer reflective film and the phaseshift film, wherein the protective film is made of a material containingsilicon (Si) and oxygen (O), and the second layer and the first layerare layered in this order on the protective film.
 5. A reflective maskcomprising: a substrate; a multilayer reflective film on the substrate;and a phase shift pattern on the multilayer reflective film, wherein thephase shift pattern is obtained by patterning a phase shift film forshifting a phase of EUV light, and the phase shift film comprises afirst layer and a second layer, the first layer comprises at least oneselected from tantalum (Ta) and chromium (Cr), and the second layercomprises ruthenium (Ru) and at least one selected from chromium (Cr),nickel (Ni), cobalt (Co), vanadium (V), niobium (Nb), molybdenum (Mo),tungsten (W), and rhenium (Re).
 6. A method of manufacturing areflective mask, the method comprising: forming a phase shift pattern bypatterning a second layer by a dry etching gas comprising achlorine-based gas and an oxygen gas and then by patterning a firstlayer by a dry etching gas comprising a halogen-based gas comprising nooxygen gas, wherein, a reflective mask blank comprises a multilayerreflective film and a phase shift film for shifting a phase of EUV lighton a substrate in this order, and the phase shift film comprises thefirst layer and the second layer, the first layer comprises tantalum(Ta), and the second layer comprises ruthenium (Ru) and at least oneselected from chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V),niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re).
 7. Amethod of manufacturing a reflective mask, wherein the first layer inthe reflective mask blank according to claim 1 comprises chromium (Cr),and a phase shift pattern is formed by patterning the second layer by adry etching gas comprising an oxygen gas and then by patterning thefirst layer with a dry etching gas comprising a chlorine-based gascomprising no oxygen gas.
 8. A method of manufacturing a reflectivemask, wherein the first layer in the reflective mask blank according toclaim 1 comprises chromium (Cr), and a phase shift pattern is formed bypatterning the second layer and the first layer by a dry etching gascomprising a chlorine-based gas and an oxygen gas.
 9. A method ofmanufacturing a semiconductor device, the method comprising thereflective mask according to claim 5 in an exposure apparatus comprisingan exposure light source that emits EUV light, and transferring atransfer pattern to a resist film formed on a transferred substrate. 10.The reflective mask according to claim 5, wherein the second layercomprises ruthenium (Ru) and at least one selected from chromium (Cr),nickel (Ni), and cobalt (Co).
 11. The reflective mask according to claim5, further comprising a protective film between the multilayerreflective film and the phase shift film, wherein the protective film ismade of a material containing ruthenium (Ru), and the first layer andthe second layer are layered in this order on the protective film. 12.The reflective mask according to claim 5, further comprising aprotective film between the multilayer reflective film and the phaseshift film, wherein the protective film is made of a material containingsilicon (Si) and oxygen (O), and the second layer and the first layerare layered in this order on the protective film.
 13. The method ofmanufacturing a reflective mask according to claim 6, wherein the secondlayer comprises ruthenium (Ru) and at least one selected from chromium(Cr), nickel (Ni), and cobalt (Co).
 14. The method of manufacturing areflective mask according to claim 6, further comprising a protectivefilm between the multilayer reflective film and the phase shift film,wherein the protective film is made of a material containing ruthenium(Ru), and the first layer and the second layer are layered in this orderon the protective film.
 15. The method of manufacturing a reflectivemask according to claim 7, wherein the second layer comprises ruthenium(Ru) and at least one selected from chromium (Cr), nickel (Ni), andcobalt (Co).
 16. The method of manufacturing a reflective mask accordingto claim 7, further comprising a protective film between the multilayerreflective film and the phase shift film, wherein the protective film ismade of a material containing silicon (Si) and oxygen (O), and thesecond layer and the first layer are layered in this order on theprotective film.
 17. The method of manufacturing a reflective maskaccording to claim 8, wherein the second layer comprises ruthenium (Ru)and at least one selected from chromium (Cr), nickel (Ni), and cobalt(Co).
 18. The method of manufacturing a reflective mask according toclaim 8, further comprising a protective film between the multilayerreflective film and the phase shift film, wherein the protective film ismade of a material containing silicon (Si) and oxygen (O), and thesecond layer and the first layer are layered in this order on theprotective film.